Induction of a deficiency of steroid delta 4-5 alpha-reductase activity in liver by a porphyrinogenic drug.

A Kappas, … , D R Bickers, A P Alvares

J Clin Invest. 1977;59(1):159-164. https://doi.org/10.1172/JCI108614.

Research Article

The hepatic enzymes that catalyze drug oxidations and the reductive metabolism of steroid hormones to 5alpha- derivatives are localized in membranes of the endoplasmic reticulum. Phenobarbital, which exacerbates acute intermittent porphyria in man, induces drug-oxidizing enzymes in liver. Additionally, patients in whome the primary gene defect (uroporphyrinogen-I-synthetase deficiency) of acute intermittent porphyria has become clinically expressed have low levels of hepatic steroid delta4-5alpha-reductase activity. This 5alpha-reductase deficiency in acute intermittent porphyria leads to the disproportionate generation of 5beta-steroid metabolites from precursor hormones; such steroid metabolites have significant porphyria-inducing action experimentally. In this study the effects of phenobarbital on drug oxidation and steroid 5alpha-reduction in man were examined to determine if this drug could produce changes in steroid 5alpha-reductase activity which mimicked those seen in patients with acute intermittent porphyria. Metabolic studies with [14C]-testosterone and 11beta-[3H]hydroxyandrostenedione were carried out in five normal volunteers. In all five subjects phenobarbital administration (2 mg/kg/per day for 21 days) enhanced plasma removal of the test drugs antipyrine and phenylbutazone as expected; but in four subjects phenobarbital also substantially depressed 5alpha-metabolite formation from [14C]testosterone and resulted in a pattern of hormone biotransformation characterized by a high ratio of 5beta/5alpha-metabolite formation. Studies with 11beta-[3H]hydroxy-androstenedione in three subjects confirmed that phenobarbital produced this high 5beta/5alpha ratio of steroid metabolism by depressing 5alpha-reductase activity for steroid hormones in liver. The […]

Find the latest version: https://jci.me/108614/pdf Induction of a Deficiency of Steroid A4-5a-Reductase Activity in Liver by a Porphyrinogenic Drug

ATTALLAH KAPPAS, H. LEON BRADLOW, DAVID R. BICKERS, and ALVITO P. ALVARES Froml Thle Rockefeller University Hospital, New York 10021

ABSTRACT The hepatic enzymes that catalyze mimicks the high 5/8/5a-steroid metabolite ratio formed drug oxidations and the redtuctive metabolism of ster- from endogenotis hormones in acute intermittent oid hormones to 5a-derivatives are localized in porphyria. The proximate mechanism by which pheno- membranes of the endoplasmic reticulum. Pheno- barbital indtuces reciprocal changes in activities of the barbital, whiclh exacerbates acute intermittent por- microsomal enzymes which catalyze drtug oxidations phyria in mnan, induices drug-oxidizing enzymes in and steroid 5a-redtictions is not known. This action of liver. Additionally, patients in whom the primary phenobarbital raises the possibility, however, that gene defect (uiroporphyrinogen-I-synthetase de- certain drugs which provoke exacerbations of htuman ficiency) of actute intermittent porphyria has become porphyria may do so, in part, by produicing de- clinically expressed have low levels of hepatic ster- leteriouis shifts in the patterns of endogenouis steroid oid A4-5a-reductase activity. This 5a-reductase de- hormone metabolism. ficiency in actute intermittent porphyria leads to the disproportionate generation of 5/3-steroid metabolites INTRODUCTION from prectursor hormones; such steroid metabolites have significant porphyria-inducing action experi- The present study was uindertaken to examine the mentally. In tlhis study the effects of phenobarbital effect of phenobarbital on steroid M4-5a-redtictase ac- on drug oxidation and steroid 5a-reduction in man tivity in normal stubjects. Phenobarbital is a proto- were examined to determine if this drtug could type of druigs known to provoke htuman as well as produice changes in steroid 5a-reductase activity which experimental hepatic porphyria and to indtuce the mimicked those seen in patients with acute inter- cytochrome P-450-dependent mixed ftinction oxidase mittent porphyria. Metabolic stuLdies with ['4C]- system in liver (1, 2). This NADPH-requiring en- testosterone and 1 1/3-[3H]hydroxyandrostenedione zyme complex localized in the membranes of the endo- were carried out in five normal volunteers. In all five plasmic retictultum mediates the oxidation of ntumerous, subjects phenobarbital administration (2 mg/kg/per day struictulrally diverse chemicals, incluiding natuLral ster- for 21 days) enhanced plasma removal of the test oid hormones (3). drugs antipyrine and phenylbutazone as expected; but The NADPH-dependent 5a-redtictase system for in four subjects phenobarbital also substantially de- steroids is also localized in the endoplasmic reticulum, pressed 5a-metabolite formation from [14C]testoster- but the effects of phenobarbital or other porphyrino- one and resulted in a pattern of hormone bio- genic drugs on its activity have not been studied transformation characterized by a high ratio of 5/3/5a- in normal individuals. Stuch sttudies couild be relevant metabolite formation. Studies with 1 1_3-[3H]hydroxy- to the interplay of drug, endocrine, and gene factors androstenedione in three subjects confirmed that which results in exacerbation of acuite intermittent phenobarbital produced this high 5f3/5a ratio of steroid porphyria (AIP)' since (a) individtuals in whom the metabolism by depressing 5ai-reductase activity for gene defect for this disorder, uroporphyrinogen I steroid hormones in liver. The high ratio of 5,8/Sa- synthetase (UROS) deficiency (4-9) has become clin- metabolites formed in normals after drug treatment ically expressed also have a significant deficiency of hepatic steroid A4-5a-reductase activity (10); and (b) Dr. A. P. Alvares is a recipient of a Research Career this Sa-reductase deficiency leads to the disproportion- Development Award, no. I K04-ES-00010, from the National Instittutes of Health. 'Abbreviations used in this p)a;)er: AIP, acute intermittent Receivedfor publication 26 Februiary 1976 auid in revised porphyria; ll-OHAD, 11-OH-androsteneclione; UROS, uro- form 13 Sep)temiber 1976. porphyrinogen I synthetase. TheJournal of Clinical Investigation Volume 59 January 1977-159-164 159 TABLE I METHODS AND RESULTS Effect of Phenobarbital Treatment on Plasma Half-Lives of Five normal volunteers (three miales, two femiales, age Antipyrine and Phenylbutazone in Normal Subjects range 25-35 yr) participated in the study; each gave in- Phenvlbutazone-plasma ti, formed consent and the experimenital plrotocol was re- Antipyrine-plasnia 11 d(a s viewed and approved hy the Rockef'eller University In- ti, stitutional Review Board. None hald received drugs within Pre- Post- Pre- Post- the 4 wk preceding the experimenits. Erytlhrocyte UROS treat- treat- treat- treatt- activities were assayed in each volunteer hy the method Stub- imienit imienit Decrease imienlt imient Decrease of Sassa et al. (8) and slhown to be witlhin the normal ject periocl period in) t1 periodl perio0( ill t range. [4-14C]Testosterone and 11-OH-[ 1,2,-3H ]androstene- dione were prepared and administered and metabolites (17 % were isolated to radiochemical purity as described in oui 1 10.0 6.3 37 2.6 2.1 19 previous studies (11, 12, 18-20). Briefly, on dclay 1 of the study, 2 5.7 3.7 35 4.5 2.0 55 an intravenous infusion of 5% glucose in water was begun and a weighed amount of radioactive testosterone was in- 3 16.5 11.0 33 2.7 1.8 33 jected into the rubber tubing immediately adljacelnt to the 4 18.0 10.5 42 2.4 2.0 17 needle and washed in with the intravenouis inf'usion over a 5 7.8 6.0 23 3.7 2.3 38 10-min period. Two complete 24-h urinie collectionis were obtained from each subject and metal)olites wer-e hydrolyzed, extracted, and isolated. On day 4 of the study radioactive 11-OH-androstenedione (11-OHAD) was simiiilarlv admin- ate generation of 5p3-metabolites from certain steroid istered intravenousily and( a subsequent 2-day urine collec- hormones and precursors in suiclh patients (11, 12). tion was obtained and analyzed as described. After these Steroids derived from the 5/3-pathway of hormone infusions the plasma half-lives of' antipyrine and phenyl- butazone were determined in eachi subject. Antipyrinie was metabolism are known to be more potent in their dissolved in a flavored syrup and(i adminiistered orally at a ability to induce porphyria in avian liver cells dose of 11 mg/kg. Blood samnples were obtained at 0, 3, 6, 9, growing in primary cultures than their 5a-epimers 12, and 15 h after ingestion ancl antipyrine meassured in (13-15). plasma samples according to the metlhod of Brodie et al. (21). We have earlier shown that AIP patients who have Phenylbutazone was administered 1 day later at a (lose of 6 mg/kg orally and plasma samples were obtained on days 0, 1, the clinically and biochemically expressed syndrome 2, 3, 4, 5, and 7. Phenylbutazone levels were determinedl generate substantially more 5/3-, than 5a-steroid according to the method of Burns et al. (22). Phenobarbital metabolites from endogenous as well as isotopically was then administered orally at niglht in a dose of' 2 mg/kg labeled precursor hormones (11, 12) than do normal for 21 consectitive days and eaclh steroid and drug metabolism study was then repeated in the samiie se(iuence except f'or two subjects; in addition Paxton et al. (16) and Goldberg subjects in wholm the 11-OHAD metabolism sttudies were et al. (17) have demonstrated tlhat AIP patients have omitted. All stuidies were carriecl ouit in The Rockefeller considerably higher levels of 5,8-steroids in their urine University Hospital. and in plasma than do normal individuals. These Antipyrine aind pheiyl1butazote metabolism7i. The restults findings suggest that the patterns of endogenous of the plasma half-life sttudies of' these drtigs in the five normal subjects before and after the phenobarbital treat- steroid metabolism, particularly the relative propor- ment period are shown in Table I. Each subject responded tion of 5,3-metabolites formed from gonadal and adrenal to phenobarbital indtuction of the microsomal enzymes steroid hormones, as well as the prodtuction rates of which mediate oxidation of these drtugs by increasinig their- such hormones may have considerable relevance to the hepatic metabolism and thus their rates of plasma removal. defect in AIP The extent of the decreases in plasma half-lives varied clinical expression of the UROS-gene for each drug from subject to subject, as did the chlanges in individuals. rates of oxidation of the two druigs by eachi individual sub- The results of the present study show that short- ject in keeping with the findings of Vesell and Page (23, 24) term treatment of normal individuals with the por- and Davies et al. (25). phyria-inducing drug, phenobarbital, leads not only to Reductive mnetabolism of [4- '4C]testosterou e. Table II provides quantitative data on the recovery of isotopically enhanced rates of oxidative drug metabolism in liver labeled metabolites from [I4C]testosterone in each of the as expected; but also to the concomitant and sig- five subjects. The total recovery of labeled derivatives varied nificant depression of activity of the hepatic A4- from individual to individual as expected btut there were ino 5a-reductase system for natural steroids and there- significant or consistent differences in total isotope recovery fore to an increase in the ratio of between the phenobarbital and conitrol periods. However, 5,8/5a-metabolites in each individtual the absolute amouint of 5an-metabolite formed from precursor hormones. Since 5/3-steroids (androsterone) formed in the phenobarbital period dleclined have potent porphyrinogenic properties, the pos- from the control period and the amouint of isotope recovered sibility is thus raised that certain drugs or other exog- in the 5,8-(etiocholanolone) metabolite or "polar" metab- enouis chemicals which provoke exacerbations of AIP olite fraction increased. In fouir of the five subjects these changes in metabolite formation resulted in a significant may do so, in part, by inducing deleterious shifts in increase in ratio of 5,3/5a-metabolites formed from the hor- the patterns of metabolism of endogenous steroid mone in the liver (26) as shown in Fig. 1. The 5,3- and hormones. 5a-compounds isolated constituite the predominant fraction of'

160 A. Kappas, H. L. Bradlow, D. R. Bickers, and A. P. Alvares recoverable metabolites derived from the biotransformation of testosterone in man (18). The left portion of Fig. 1 shows for comparative purposes the 5,3/5a-metabolite ratios in a group of 13 normal subjects and 15 AIP patients studied earlier in identical metabolic studies with the radiolabeled hormone (11). One subject (subject 5, Table II) showed no significant change in the ratio of 5/3/5a-metabolites formed from testosterone after drug treatment although a significant 0 increase in polar metabolites did result from phenobarbital administration. These polar compounds are a mixture pri- marily of C18 and C7 (,8) hydroxy derivatives of testos- a) terone, the bulk of which are 5,8-compounds (27). Such metabolites normally comprise less than 4% of the total -0 recoverable urinary radioactivity from administered [4-14C ]- 4-a) testosterone in man (see Table II). In these studies the percent of polar compounds increased above 7% in the drug treatment period as compared to the control period in only one Qz1tuu subject (Table II). Reductive metabolism of [1,2-3H]11-OHAD. To deter- mine whether the increase in 5,3/5a-ratio of metabolites formed from [4-14C]testosterone (Fig. 1) after phenobarbital administration may have resulted from a relative deficiency of steroid A4-5a-reductase activity, studies of [1,2,-3H ]- l1-OHAD disposition in three of the four normal subjects who demonstrated this shift in metabolism (subjects 1-3, Fig. 1) were carried out. The principal metabolite recovered in the urine from 11-OHAD in man is the 5a-compound 1l-hydroxyandrosterone. The 5,/-metabolites, 1 1-hydroxy- etiocholanolone, and 1l-keto-etiocholanolone form only a small fraction of transformation products from 11-OHAD (usually less than 5-10%/c) (19, 20). The latter compounds Normals AIP Normals Normals do not increase in conditions in which steroid A4-5a-re- (Control) (Barbiturate) ductase is depressed; instead a direct reduction of the C3 ketone to a C3-hydroxyl takes place and the double bond FIGURE 1 Ratios of 5,8/5a-metabolites formed from [14C]- at C4-5 remains chemically intact (12, 20). This pattern of testosterone. The ranges of 5,3/5a-metabolite ratios found in groups of normal individuals and in patients with clin- ically expressed AIP are shown on the left. These data were obtained in earlier studies. The specific ratios in the five TABLE II normal subjects in this study during control periods and Effect ofPhenobarbital Treatment on the Metabolism of [14C] after phenobarbital are shown on the right. Subjects 1-4 Testosterone to Androsterone, Etiocholanolone,* showed a substantial increase in the fraction of hormone and Polar Metabolites metabolized along the 5,3-pathway; the 53/5ac-ratio in subject 5 did not change. Steroid metabolites isolated Subject Period At El Polart l1-OHAD metabolism reflects the fact that the Cll-hydroxy substituent of this C19 hormone appears to inhibit its reduction by the 5,8-steroid reductase in contrast to the ability 1 C 32.7 20.8 2.9 of Cll-deoxy steroids such as testosterone and dehydro- p 9.0 32.0 3.4 isoandrosterone to serve equally as substrates for both the 5a- and the 5,8-steroid reductases. 2 C 24.9 26.5 2.7 The results of the metabolic studies with 1l-OHAD in the three normal subjects before and after phenobarbital are P 11.8 35.6 6.8 shown in Fig. 2, with the data expressed, as in previous studies, as the percent 5a-metabolism of ll-OHAD of the 3 C 16.9 18.0 3.2 total fraction of identifiable metabolites formed from the P 9.7 20.1 3.7 hormone. Earlier data from similar metabolic studies in 13 normal and 7 AIP subjects (12) are shown in Fig. 2 for 4 C 14.7 19.2 0.5 comparative purposes. All three subjects stuLdied showed a P 10.2 19.2 4.1 decrease in 5a-reductive metabolism of 11-OHAD after phenobarbital (Fig. 2). 5 C 15.9 25.8 3.9 These data parallel our earlier findings in AIP patients ex- cept that in the latter subjects, the 5a-reductase de- P 12.2 17.6 20.4 ficiency for 11-OHAD and for testosterone was more profound (and was demonstrated in the absence of drug treatment); * A, 5a, androsterone; E, 5,B, etiocholanolone; C, control and the output of A4-3ca-OH-metabolites was greater (12). period; P, phenobarbital period. Erythrocyte UROS activity did not change in any subject t Percent of administered dose as recovered metabolite. after phenobarbital treatment. Depression of Steroid A4-5a-Reduction by Phenobarbital 161 along the 5a-path way. Depression of 5a-redtictase 90 activity by phenobarbital resuilted, in the case of this hormone, in a decrease in formication of its maiin metaboli te, 1 13-hydroxyandrosterone aind ain iincreatse in excretion of 11-OHAD metabolites in which thle C4-5 double bond remaineid intact. The C1I-hvdroxvl 70 stubstitLent of this hormiionie as noted above blocks its compensatory metabolismii by the 5/3-steroid re- 0 dtuctase. These findings provide firm evidence thalt the E activity of' steroid A4-5a-redtuctase in liver is depressed .LI) by phenobarbital. -0 50 - The data recorded in Table I and Fig. 1 indicate 0 U). that reciprocal changes in the rates of steroid re- d duiction along the 5a-pathway and the rates of' druig oxidation ocecurred in fouir of' the five suibjects stuLdied after treatment with pIhenobarbital. Plheno- 30H barbital is known to indtuce activity of' the lhepatic mixed ftunction oxidase systemii f'or drtugs buit thie reason why the drug concurrently prodtuces depres- sion of steroid 4-5ay-reductiase activity in miian is not known. This effect could result from a variety of' meclh- 1o0 anisms but it cannot wholly be due to competitive diversion of lhormonal substrate f'rom the 5(t-reductase to the steroid hydroxylase system in liver sinice in one of the Normals A P only fiv/e individtuals studied (Table II) Normals Normals did the fraction of' polar metabolites incirease suib- (Control) (Barbiturate) stantially. FIGURE 2 Percent 5a-metabolism of [3H] 11-OH-andro- The ability of phenobarbital to depress thie 5(v- stenedione. The ranges of values for the percent 5a- reduction of steroid hormonies in normiials and tlhus to metabolism of this hormone in groups of normal individuals produce a higlher ratio of 5/3/5a-metabolite and AIP patients obtained in earlier studies are shown on f'ormu-ationi the left. The specific values obtained in this study before from certain hormonie substr'ates mimiicks the p1atterin and after phenobarbital treatment of subjects 1-3 are shown of excessive generation of 5/3-steroid metal)olites on the right. In all three stubjects, phenobarbital decreased which characterizes AIP patients in whomii the por- the rate of formation of 5a-metabolism of the hormone. phyric syndrome hals become clinically anid biochbem- ically expressed (11, 12). This drug effect mnay thus DISCUSSION hlave some relevaince to the miiechalinismii of' pheno- barbital-induced exacerbations of' AIP. In tissuie cul- The present stuidy demonstrates that admiiinistration tired avian embryo liver 5(3-steroid metabolites aire of' the porplhyria-indtucing drtug, ph enobarbital, to nor- more potent porplhyriinogenic agents thaln their 5(t- mal subjects can significantly alter the pattern of' re- epimers, alth oughi the latter compouinds (1(lo isplay dtuctive metabolismii of nattural steroid lhormioies, while clear porphyrin-inducing activity in this preparation as simtultaneotusly enhancing the mixed f'tunction oxida- we halve showni earlier (13, 14). In rat liver 5a- tion of drugs stuch as antipyrine and phenylbtutazone. metabolites have equal or greater potency in in- In the case of testosterone, phenobarbital induced a ducing 6-aminolevtulinate synthetase (28) thtus stig- shift in the pattern of redtuctive metabolism of the C4- gesting the possibility of' a species depenidenice of' 5 double bond such that the ratio of 5/3/5a-metabolites the potency of 5/3- and 5a-steroids in iniultcinig formed from the hormone increased significantly. This experimental h epati c porplhyria. Neverthleless, in pa- higher 5,8/5a-metabolite ratio resulted principally from tients with clinically expressed AIP hligh ratios depressed activity of the 5a-reductase for the hor- (ranging from 50 to 1,000% above the miiean niormal mone; as a consequience of this effect, a relatively ratio [11]) of' 5/3/5a-metabolismn of' endogenons as greater fraction of tl-he C4-5-reductive metabolism of well as tracer-labeled steroid lhormonies have beeni the hormonal stubstrate took place via the steroid demonstrated in ouir earlier sttudies; anid Goldberg A4-5,/-reductase in cytosol as compared with the mem- and associates (16, 17) have slhown that AIP pa- brane-bound steroid A4-5a-reductase. This was con- tients excrete excessive amouniits of' 5/3-steroids in firmed by the sttudies with 11-OHAD an adrenal hor- uirine and have considerably greater than normal levels mone whose reductive metabolism takes place largely of 5,/-steroids in their plassmas. These findings thlus 162 A. Kappas, II. L. Bradlow, D. R. Bickers, and A. P. Alvares conform with our earlier suggestion that the greatly S. Marver. 1972. Intermittent acute porphyria-demon- increased production of steroid hormones as well as stration of a genetic defect in porphobilinogen me- tabolism. N. Engl. J. Med. 286: 1277-1282. the ratio of 5,/- and 5ai-metabolites formed from 6. Miyagi, K., R. Cardinal, I. Bossenmaier, and C. J. these precursors in the liver may bear significantly Watson. 1971. The serum porphobilinogen and hepatic on the mechanism of endocrine-related activation of porphobilinogen deaminase in normal and porphyric AIP (29) at or near puberty. While phenobarbital, as a individuals. J. Lab. Clin. Med. 78: 683-695. 7. Strand, L. J., U. A. Meyer, B. F. Felsher, A. G. prototypic porphyrinogenic agent, clearly can provoke Redeker, and H. S. Marver. 1972. Decreased red cell experimental hepatic porphyria directly in tissue cul- uroporphyrinogen I synthetase activity in intermittent tture (1), the fact that it can also slhift endogenous acute porphyria. J. Clin. Invest. 51: 2530-2536. steroid metabolismii in man towards a presumably 8. Sassa, S., S. Granick, D. R. Bickers, H. L. Bradlow, and deleterious pattern (i.e. relatively more 5/3-steroid as A. Kappas. 1974. A microassay for uroporphyrinogen I synthetase, one of three abnormal enzyme activities in compared with Sa-steroid formatioon) suggests an acute intermittent porphyria, and its application to the additional mechanism by which this and related study of the genetics of this disease. Proc. Natl. Acad. drigs might provoke AIP in genetically susceptible Sci. U.S.A. 71: 732-736. individuals. 9. Sassa, S., G. Solish, R. D. Levere, and A. Kappas. 1975. Studies in porphyria. IV. Expression of the gene defect In considerinig the possibility of some type of inter- of acute intermittent porphyria in cultured human skin actioin between chemical, hormonal, and genetic fibroblasts and amniotic cells: prenatal diagnosis of factors in activating AIP it should be recalled that while the porphyria trait.J. Exp. Med. 142: 722-731. clinically manifested AIP occurs only at or after puberty, 10. Kappas, A., H. L. Bradlow, P. N. Gillette, R. D. Levere, the UROS-deficiency characterizing patients with this and T. F. Gallagher. 1972. A defect of steroid hormone metabolism in acute intermittent porphyria. Fed. Proc. 31: disease can be identified in utero (9) as well as in all 1293- 1297. prepubertal and adult gene carriers of the AIP trait even 11. Kappas, A., H. L. Bradlow, P. N. Gillette, and T. F. though the defect remains entirely latent (8, 29). Since Gallagher. 1972. Studies in porphyria. I. A defect in the it is extremely unlikely that completely latent AIP gene reductive transformation of natural steroid hormones in the hereditary liver disease, acute intermittent porphyria. carriers escape all exposure to drugs and other J. Exp. Med. 136: 1043-1053. porphyrinogenic chemicals it is reasonable to suppose 12. Bradlow, H. L., P. N. Gillette, T. F. Gallagher and A. that clinical penetrance of the UROS-gene defect is Kappas. 1973. Studies in porphyria. II. Evidence for a determined, in part, by a congeries of "metabolic" deficiency of steroid .X4-5a-reductase activity in acute (including environmental and nutritional) factors, of intermittent porphyria. J. Exp. Med. 138: 754-763. 13. Granick, S., and A. Kappas. 1967. Steroid induction of which the chemical-endocrine interaction- described porphyrin synthesis in liver cell culture. I. Structural in this study may be an example. basis and possible physiological role in the control of heme formation.J. Biol. Chem. 242: 4587-4593. ACKNOWLEDGMENTS 14. Kappas, A., and S. Granick. 1968. Steroid induction of porphyrin synthesis in liver cell culture. II. The effects The authors are indebted to Miss Ann Marie Quatela of heme, uridine diphosphate glucuronic acid, and in- for preparation of the manuscript. hibitors of nucleic acid and protein synthesis on the This study was supported in part by National Founda- induction process.J. Biol. Chem. 243: 346-351. tion grant 1-350; National Institutes of Health granit ES-01055; 15. Kappas, A., C. S. Song, R. D. Levere, R. A. Sachson, and a gift from the Scaife Family Trust. and S. Granick. 1968. The induction of 6-aminolevulinic acid synthetase in vivo in chick embryo liver by nattural steroids. Proc. Natl. Acad. Sci. U.SA. 61: 509-513. REFERENCES 16. Paxton, J. W., M. R. Moore, A. D. Beattie, and A. 1. Granick, S. 1966. The induction inl vitro of the synthesis Goldberg. 1974. 17-Oxosteroid conjugates in plasma and of 6-aimiinolevulinic acid synthetase in chemical urine of patients with acute intermittent porphyria. Clin. porphyria: a response to certain drugs, sex hormones, Sci. Mol. Med. 46: 207-222. and foreign chemicals. J. Biol. Chem. 241: 1359-1375. 17. Goldberg, A., M. R. Moore, A. D. Beattie, P. E. Hall, 2. Cucinell, S. A., A. H. Conney, M. Sansur, and J. J. J. McCallum, and J. K. Grant. 1969. Excessive urinary Burns. 1965. Drug interactions in man. I. Lowering ef- excretion of certain porphyrinogenic steroids in human fect of phenobarbital on plasma levels of bishydroxv- acute intermittent porphyria. Lancet. 1: 115- 118. coumarin (Dicumarol) and diphenylhydantoin (Dilantin). 18. Gallagher, T. F., H. L. Bradlow, D. K. Fukushima, C. Clin. Phlarmnacol. Ther. 6: 420-429. T. Beer, T. H. Kritchevsky, M. Stokem, M. L. Eidinoff, 3. Conney, A. H. 1967. Pharmacological implications of L. Hellman, and K. Dobriner. 1954. StuLdies of the microsomal enzyme induction. Pharmnacol. Rev. 19: metabolism of isotopic steroids in man. Recentt Prog. 317- 366. Horni. Res. 9: 411-434. 4. Strand, L. J., B. F. Felsher, A. G. Redeker, and H. S. 19. Bradlow, H. L., and T. F. Gallagher. 1957. Metabolism Marver. 1970. Heme biosynthesis in intermittent acute of 11,83-hydroxy-_4-androstene-3,17-dione in man. J. Biol. porphyria: decreased hepatic conversion of porphobilin- Chem. 229: 505-518. ogen to porphyrins and increased delta aminolevulinic 20. Bradlow, H. L., B. Zumoff, D. K. Fukushima, L. Hellman, acid synthetase activity. Proc. Natl. Acad. Sci. U.S.A. and T. F. Gallagher. 1966. Metabolism of 11,-hydroxy- 67: 1315-1320. A4-androstene-3,17-dione: Effect of thyroid hormone. 5. Meyer, U. A., L. J. Strand, M. Doss, A. C. Rees, and H. J. Clin. Endocrinol. Metab. 26: 949-954. Depression of Steroid A4-5a-Reduction by Phenobarbital 163 21. Brodie, B. B., J. Axelrod, R. Soberman, and B. B. Levy. M. Orme. 1973. Interindividual differences in rates of 1949. The estimation of antipyrine in biological ma- drug oxidation in man. Drug Metab. Dispos. 1: 411-417. terials.J. Biol. Chem. 179: 25-29. 26. Bardin, C. W., and J. A. Mahouideaui. 1970. Dynamics of 22. Bturns, J. J., K. R. Rose, T. Chenkin, A. Goldman, A. androgen metabolism in women with hirsutism. Ann. Schulert, and Brodie, B. B. 1953. The physiological Clin. Res. 2: 251-262. disposition of phenylbutazone (Buitazolidin) in man and a 27. Fukushima, D. K., H. L. Bradlow, L. Hellman, and T. F. method for its estimation in biological material. J. Gallagher. 1962. Isolation and characterization of 18- Pharmacol. Exp. Ther. 109: 346-357. hydroxy-17-keto-steroids.J. Biol. Chem. 237: 3359-3363. 23. Vesell, E. S., and J. G. Page. 1968. Genetic control of 28. Edwards, A. M., and W. H. Elliott. 1975. Indtuction of drug levels in man: phenylbtutazone. Science (Wash. 8-amino-levulinic acid synthetase in isolated rat liver D.C.). 159: 1479-1480. cells by steroids. J. Biol. Chem. 250: 2750-2755. 24. Vesell, E. S., and J. G. Page. 1968. Genetic control of 29. Kappas, A., S. Sassa, and S. Granick. 1974. Endocrine- drug levels in man: antipyrine. Science (Wash. D.C.). gene interaction in the pathogenesis of acute intermittent 161: 72-73. porphyria. Res. Publ. Assoc. Res. Nerv. Ment. Dis. 53: 25. Davies, D. S., S. S. Thorgeirsson, A. Breckenridge, and 225-237.

164 A. Kappas, H. L. Bradlow, D. R. Bickers, and A. P. Alvares