Pediatr. Res. 15: 0019-0021 (1981) glucocorticoids

Constriction of the Fetal Ductus Arteriosus by Glucocorticoid Hormones

KAZUO MOMMA."" SHIGETAKE NISHIHARA, AND YACHIO OTA Section of Pediatric Cardiology, The Institute of Japan. Tokyo Women's Medical College, Tok-yo. Japan

Summary within 5 sec after delivery by the rapid whole-body freezing technique using acetone cooled to -80°C by dry ice (9). Body Hydrocortisone, prednisolone, and betamethasone were injected weight of was measured in the frozen state to assess fetal into a rat that was 21 days pregnant, and the fetal ductus arteriosus maturation. The thorax of the frozen fetus was trimmed and was studied using the rapid whole-body freezing technique. All sectioned on the freezing microtome (23) to obtain transverse these glucocorticoids constricted the fetal ductus arteriosus in a sections of the main (PA) and the ductus dose-dependent relationship. Fetal ductal constriction was maxi- arteriosus (DA). The inner diameter of these vessels were mea- mum 1 to 4 hr after injection and was significantly more prominent sured with the binocular microscope (24) and micrometer (25). in premature fetuses than in mature ones. The inner diameter of the proximal, middle, and distal part of the ductus was measured, and the minimal ductal diameter was Speculation divided by the diameter of the main pulmonary artery to get DA/ Glucocorticoids may be useful in constricting the patent ductus PA ratio, which was used to determine the effect of glucocorticoids. arteriosus in the premature babies in place of indomethacin, which Various doses of hydrocortisone (1 to 1000 mg/kg), predniso- is contraindicated in the presence of renal failure or jaundice. lone (0.1 to 1000 mg/kg), and beta methasone (0.001 to 100 mg/ Administration of glucocorticoids to the mother may cause fetal kg) were injected into 27 pregnant rats on the 2 1st day of gestation, ductal constriction and fetal distress. and the fetal ductal size was studied at 4 hr after injection. Influence of gestational age on the effect of glucocorticoids on intrauterine ductal size was studied as follows. Hydrocortisone ( I0 Recent advances in research on have clarified mg/kg). prednisolone. or betamethasone was injected into four their physiologic and pharmacologic effects on the fetal and pregnant rats on the 19th day. and fetal ductal sizes studied 4 hr neonatal ductus arteriosus, whereas inhibitors of after injection were compared with those ductal sizes in the synthesis such as indomethacin and aspirin have been proved to experiment on 21st day of gestation. be effective in treatment of patent ductus arteriosus in the pre- Control values were obtained by determining fetal ductal size mature baby (6, 7). These prostglandin inhibitors, administered to on the 19th and 21st day of gestation in two rats who did not the pregnant animal or directly to the fetus, constricted the fetal receive any medication. Six pregnant rats were allowed to deliver ductus arteriosus in experimental animals (1 1, 18, 20). The glu- spontaneously on the 21st or 22nd day of pregnancy to obtain cocorticoids, another group of drugs which have anti-inflamma- normal in the rat. Fetal vitality was checked by tory action, have recently been shown to inhibit prostaglandin observing active movement of the extremities and gasping move- synthesis through inhibition of the release of prostaglandin pre- ment of the jaws just before freezing and microscopic observation cursors such as arachidonic acid (8, 10). These actions, which are of the appearance of a round. unfolded and pulmonary similar to those of nonsteroidal anti-inflammatory drugs (20), artery on the frozen section of the fetal thorax. Only those animals suggest the possibility that glucocorticoids might induce ductal with vital findings were included in this study. Two-tailed un- closure. Two clinical observations suggested ductus-constricting paired Student's I test was used for statistical analysis to determine effect of glucocorticoids (5,21), but this effect has not been proved the significance of the difference of mean values. definitely yet. For these reasons, we examined the effect of glu- cocorticoids on the ductus arteriosus of the rat fetus. RESULTS

MATERIALS AND METHODS Time of onset and duration of effects of hydrocortisone. pred- nisolone, and betamethasone on fetal ductal size in the rat is Wistar rats were raised in separate cages and fed with commer- shown in Figure I. Fetal ductal constriction began in the first hr cially obtained solid foods. Animals were mated overnight from after injection in all glucocorticoids (P< 0.05). Maximum fetal 3 PM, and vaginal smears were checked at 9 AM the next morning. ductal constriction occurred at 1 to 4 hr after injection of hydro- Pregnancy 0 day was defined by the presence of sperm on vaginal cortisone, at 2 hr after iniection of prednisolone. and at 4 hr after smear. injection of betamethasoie. Mild bit significant ( P < 0.05) ductal Time of onset and duration of effect of hydrocortisone sodium constriction persisted at 24 hr after injection of each glucocorti- hemisuccinate (125 mg/ml in distilled water; Japan Upjohn Ltd., coids. Tokyo, Japan), prednisolone acetate (I0 mg/ml in distilled water; The effects of various doses of hydrocortisone. prednisolone, Shionogi Pharmaceutical Co., Tokyo. Japan), and betamethasone and betamethasone on fetal ductal size in the rat are shown in disodium phosphate (2 mg/ml in distilled water; Shionogi Phar- Figure 2. These dose-effect curves showed that a massive dose of maceutical Co.) on intrauterine ductal size in the rat was studied each glucocorticoid resulted in complete constriction of the fetal as follows. Hydrocortisone (10 mg/kg). prednisolone ( 10 mg/kg), ductus arteriosus. Relative potency of the ductus-constricting ef- or betamethasone (0.2 mg/kg) was injected into the dorsum of the fect of hydrocortisone. prednisolone. and betamethasone was thorax of 17 pregnant rats on the 21st day of gestation. Animals roughly 1:2:20. Vital signs. behavior. and activity of the rat and were sacrificed 1, 2, 4, 8, and 24 hr later by cervical dislocation, fetus were unchanged after injection of each glucocorticoid except and fetuses were delivered quickly by cesarean section and fixed for one rat which became dyspneic and collapsed at 4 hr after MOMMA ET AL.

mant SEM I 1 number of rn8nub Influence of gestational age on the effect of hydrocortisone. prednisolone, and betamethasone on fetal ductal size in the rat is shown in Figure 3. Each glucocorticoid showed stronger ductal constriction in premature fetuses of the 19th day of gestation than in mature ones, and these differences were statistically significant ( P < 0.05). DISCUSSION The present study shows that glucocorticoids administered to the pregnant rat constricts the fetal ductus arteriosus. Glucocorti- coids administered to the pregnant rat transfer through the pla- centa to the fetus (17). The mechanism of ductal constriction in the fetus in response to glucocorticoids is not clear, but presumably is due to inhibition of phospholipase A.L.thereby inhibiting release A -A +F- of arachidonic acid and formation of prostaglandins (8, 14, 20). 0~oiii~5ie24Alteration of steps further along also could play a role. Inhibition hours after lnject~on of fetal prostaglandin formation by administration of indometh- Fig. I. Time of onset and duration of effect of hydrocortisone (10 mg/ acin or acetylsalicylic acid to the pregnant animal causes constric- kg), prednisolone (10 mg/kg), or betamethasone (0.2 mg/kg) on the fetal tion of the fetal ductus arteriosus (1 1. 16, 18). The greater con- ductus arteriosus in the rat. DA/PA, ductus arteriosus/main pulmonary stricting effect of corticosteroids in the less mature animal is artery. similar to that described for indomethacin and fetal lamb (2). Clyman et al. (3) showed that the ductus of the immature fetal mean: SEM lamb is more sensitive to the dilating action of prostaglandins ( I mmbcr ol anmnals than the ductus of the mature fetal lamb. These comparable results *Om P<005 are compatible with the hypothesis that ductus-constricting effects control of glucocorticoids are due to inhibition of prostaglandin formation 1.01 'lo' in the fetus. Glucocorticoids have been used to accelerate maturation of the fetal lung and to prevent hyaline membrane disease (1, 12, 18, 19). For this purpose betamethasone (0.2 mg/kg) or the same dose of dexamethasone was injected intramuscularly to pregnant women with premature labor (12, 15, 19). Our present study shows that such treatment may cause fetal ductal constriction and pos- sibly some fetal distress. One clinical report has demonstrated increased fetal death and distress, as well as placental insufticiency in the offspring of mothers who received prednisolone therapy

- ~ ~.-- during pregnancy (22), although such results have not been ob- lo-' lo-' served by others. Further careful study is needed to clarify the Dose : mglkg possible effect on the (4. 13). Fig. 2. Effect of various doses of hydrocortisone, prednosolone, and The present study suggests that glucocorticoids may be useful betamethasone on fetal ductus arteriosus in the rat. DA/PA. ductus to close the patent ductus arteriosus in clinical situations. At the arteriosus/main pulmonary artery. present time, indomethacin is used to treat the premature baby with patent ductus arteriosus, congestive , and respi- ratory distress syndrome. In some situations, such as in the pres- ence of renal failure or jaundice, indomethacin is contraindicated. and glucocorticoids might be safely used in its place. The duration of the effect of glucocorticoids is shorter than that of indomethacin, and more frequent administration is necessary. Glucocorticoids may induce harmful effects such as decreased resistance to infec- tion, disturbance of plasma electrolites, or hypertension. The dose of glucocorticoids remains to be determined. Although massive doses of glucocorticoids are needed to constrict the fetal ductus completely in this study, a smaller dose might be sufficient to constrict the ductus arteriosus if these glucocorticoids were admin- istered directly to the baby. CONCLUSION Glucocorticoids constrict the ductus arteriosus of the rat fetus. Birth Wcight (gm) This effect is dose dependent. Ductus constricting potency ratio of hydrocortisone, prednisolone. and betamethasone is approxi- Fig. 3. Influence of gestational age on the effect of glucocorticoids on fetal ductus arteriosus in the rat. Comparison of effects of 10 mg/kg of mately 1:2:20. Fetal ductus arteriosus constricts and closes com- pletely if glucocorticoids are injected into the pregnant rat in hydrocortisone, prednisolone, or betamethasone in preterm rats of 19 days massive dosage. The effect is maximal I to 4 hr after injection and gestation and in term rats of 21 days. DA/PA. ductus arteriosus/rnaln artery. persists more than 24 hr. Ductus-constricting effect of glucocorti- coids is more potent on premature fetuses than on mature ones.

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