Antithyroid Activity Elicited by the Ingestion of Pure Progoitrin, a Naturally Occurring Thioglycoside of the Turnip Family
Total Page：16
File Type：pdf, Size：1020Kb
ANTITHYROID ACTIVITY ELICITED BY THE INGESTION OF PURE PROGOITRIN, A NATURALLY OCCURRING THIOGLYCOSIDE OF THE TURNIP FAMILY Monte A. Greer, J. M. Deeney J Clin Invest. 1959;38(9):1465-1474. https://doi.org/10.1172/JCI103923. Research Article Find the latest version: https://jci.me/103923/pdf ANTITHYROID ACTIVITY ELICITED BY THE INGESTION OF PURE PROGOITRIN, A NATURALLY OCCURRING THIOGLYCOSIDE OF THE TURNIP FAMILY * By MONTE A. GREER AND J. M. DEENEY (From the Dizvsion of Endocrinology, Department of Medicine, University of Oregon Medical School, Portland, Ore.) (Submitted for publication March 17, 1959; accepted April 2, 1959) Foodstuffs of various sorts have been implicated The original studies of the antithyroid activity as a cause of goiter for many years. Only by the of foods in man had indicated that cooking would discovery of Chesney, Clawson and Webster in usually destroy the potency of rutabaga and 1928 that cabbage feeding would result in thyroid turnip. Goitrin also could not be isolated from enlargement in laboratory animals (1) were these cooked material but would appear when such vague hypotheses started on a firm experimental preparations were treated with myrosin (9). footing, however (for detailed review see Ref- This led to the assumption that the precursor, erence 2). called "progoitrin," could be hydrolyzed only by Although various articles of diet have been re- the myrosin contained in the crucifer and that ported to produce goiter in diverse animal species cooking, by denaturing the enzyme, would prevent since that time, studies employing the acute in- the active goitrin from being formed. Thus only hibition of thyroidal radioiodine accumulation indi- the ingestion of raw rutabagas or turnips was cated that only a relatively small number of foods considered as potentially leading to the develop- possessed antithyroid activity in man (3). Of ment of goiter (9). these, rutabaga was consistently the most potent. Recently the isolation and identification of pro- Eventually it was possible to isolate and identify goitrin as a thioglycoside has been accomplished the active agent in this species, 1-5-vinyl, 2-thio- (5). A relatively simple method of preparing oxazolidone (4), more recently termed "goitrin" sizable amounts of pure, crystalline progoitrin by (5). Goitrin has been identified in the seeds of elution from an anion exchange resin has been most Brassicae but until recently in the edible devised. This has permitted an experimental ex- parts of only rutabaga and turnip. It has now amination of our original hypothesis. To our been reported that goitrin has been detected in the surprise, we have found that progoitrin can be edible portions of cabbage, kale and rape (6, 7). converted quantitatively to goitrin in the body by As yet no other naturally occurring antithyroid both man and rats without the addition of exogen- compound with pathogenetic significance for man ous myrosin. is known to exist. Very early in the studies isolating goitrin it MATERIALS AND METHODS became apparent that this substance did not exist Crystalline progoitrin was prepared from a 75 per cent acetone extract of ground rutabaga or kale seed by elu- in the free state but was bound to a precursor tion with sodium chloride from an anion exchange col- from which it could be liberated by a crude en- umn. The method is to be presented in full in a sepa- zyme preparation, myrosin, prepared from cruci- rate paper (10). Purified goitrin and myrosin (8) were fers. Myrosin supposedly is or contains a specific also prepared from rutabaga seed. Goitrin was assayed in biological fluids by extracting thioglycosidase which hydrolyzes mustard oil with peroxide-free ether, evaporating the ether extract, thioglycosides (8). dissolving the residue in distilled water and reading the absorption at 230, 240 and 250 m, in a Beckman spec- * Supported in part by United States Public Health trophotometer. Goitrin has a maximum specific absorp- Service Grants A-2503 and A-1447. Presented in part tion at 240 m, (4) as compared to 227 for progoitrin at the 1958 Meeting of the Western Society for Clinical (5). In addition to the different absorption maxima Research. Greer, M. A., and Deeney, J. M. Physiologic they are easily distinguished by the fact that goitrin is studies with pure crystalline progoitrin. Clin. Res. 1958, equally soluble in ether and water while progoitrin is in- 6, 90. soluble in ether. 1465 1466 MONTE A. GREER AND J. M. DEENEY Acute tests of antithyroid activity in man were made In one patient with untreated recurrent Graves' dis- by two methods. In one a modification of the technique ease, a single dose of 1 Gm. progoitrin was given once of Stanley and Astwood (11), utilizing a change in the daily over a period of one month to evaluate its efficacy slope of the "accumulation gradient," was employed. in the treatment of thyrotoxicosis when administered in Ten /Ac. of 1131 was administered to subjects and counts this manner. made over the thyroid region with a collimated scintilla- The antithyroid potency of progoitrin was also tested tion counter every 10 to 20 minutes for the first four in 100 to 120 Gm. male Holtzman rats. It was given hours and every 45 to 60 minutes for the next four hours. orally, subcutaneously or intraperitoneally in physio- A final reading was taken at 24 hours. Counts taken logic saline at various intervals prior to administration over the lower thigh were assumed to represent back- of 0.2 /Ac. in 0.2 ml. physiologic saline intraperitoneally. ground and were subtracted from the neck radioactivity The animals were killed four and one-half hours after at each interval. Each corrected neck count was plotted receiving radioiodine, the thyroids dissected and their as per cent of the administered dose on the ordinate radioactivity determined in a well scintillation counter. against the square root of the time in minutes from administration of the radioiodine on the abscissa. From RESULTS such a plot a straight line is formed which persists for the first eight to 12 hours. After the slope of the accumu- I. Studies in man lation gradient had been determined, progoitrin with or without added myrosin was administered orally. Anti- A. Acute inhibition of radioiodine uptake. The thyroid activity could be detected by a deviation of the inhibition of the "accumulation gradient" follow- subsequent neck counts below the extrapolated slope. In ing the ingestion of 0.5 to 2.0 Gm. of progoitrin addition, the expected 24 hour uptake, as calculated by a previously determined formula using the slope of the orally was studied in one thyrotoxic and seven accumulation gradient (12) was compared with that euthyroid volunteers. The results are sum- actually obtained. marized in Table I and in Figures 1 and 2. In The second method employed an initial 24 hour thy- five of these subjects, myrosin was given in addi- roidal radioiodine uptake. Progoitrin was then adminis- tion at the same time; in two of these five the tered orally and followed by a second 24 hour uptake study one to three hours later. Urine was collected quan- progoitrin had been incubated with myrosin over- titatively and assayed for goitrin by the method described night at 37° in a pH 5.6 phosphate buffer. The above. Blood was also drawn for goitrin assay at vari- degree of inhibition of the accumulation gradient ous intervals before and after administration of progoitrin. was arbitrarily graded from zero to five according In two subjects, purified but noncrystalline goitrin was to the system previously used (3). given to compare its metabolism and activity with pro- goitrin. It is apparent that inhibition of the acute up- In three patients, progoitrin was administered through take of radioiodine was produced by the ingestion a 30 cm. rectal tube. The patients were placed in a of progoitrin. Prior incubation of progoitrin with prone position with the trunk flexed downward almost myrosin or the addition of this enzyme at the 90° over the edge of the table. Progoitrin was dissolved of administration did not seem to in 20 ml. of saline and allowed to flow into the colon by time progoitrin gravity. Two successive rinsings, each with 20 ml. sa- affect the results materially. line, were then made through the tube. The interval from ingestion of progoitrin to a TABLE I Inhibition of accumulation gradient by oral progoitrin (PG) in euthyroid patients * Accumu- lation Expected 24 Actual 24 Grade of Patient gradient Interval Dose PG Myrosin hr. uptake hr. uptake inhibitiont min. Gm. W. H. 1.28 216 0.5 34.6 24.5 2 M. K. 1.28 139 0.5 + 34.6 26.6 2 C. K. 1.95 95 2.0 + 48.4 22.5 5 M. M. 1.20 166 2.0 + 32.7 16.1 5 A. K. 1.37 116 2.0 36.6 18.8 5 M. L. 0.58 251 2.0 17.0 10.5 5 L. R. 0.68 104 2.0 19.7 12.0 5 * Interval = time from administration of progoitrin to beginning inhibition of radioiodine uptake. Ten ml. myrosin was given with progoitrin where indicated. t Grade of inhibition is based on a scale of 0 = no effect and 5 = complete inhibition for 24 hours (3). t Myrosin was incubated with progoitrin for 18 hours before administration. ANTITHYROID ACTIVITY OF PROGOITRIN 1467 INHIBITION OF ACCUMULATION GRADIENT BY PROGOITRIN IN A EUTHYROID PATIENT, C. K. @1 0 12 0 0 PG+M So 20 I, 1 a25 5 I. lC1 D 5 I I LI AIC 2 4 6 8 10 12 14 16 18 20 24 N/(time in minutes hrs. FIG. 1. INHIBITION OF ACCUMULATION GRADIENT BY SIMULTANEOUS ORAL ADMINISTRATION OF 2 GM.