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Thecal cell 3-beta hydroxysteroid dehydrogenase activity: modulation by human chorionic gonadotropin, progesterone,
Abstract:
Thecal cell steroidogenesis plays a major role in folliculogenesis within the porcine ovary. Accordingly, the effects of physiological concentrations of steroids on 3 beta-hydroxysteroid dehydrogenase activity (3 beta-HSD) were determined. Theca was excised from large porcine follicles and prepared in a monolayer culture in 1 ml of serum-free media. Cells were treated 24 h after culture as follows: (1) control, (2) hCG (5 IU); (3) progesterone (P, 3 micrograms); estradiol-17 beta (E, 4 micrograms); 5 beta-dihydrotestosterone (DHT, 1 microgram); (4) hCG + P or E or DHT. At 3, 6, 12, 24 and 48 h after treatment, media were assessed for P levels. For 3 beta-HSD activity, P formation by microsomal fractions incubated with 1 microM pregnenolone + 5 microM NAD+ for 1 h (37 degrees C) was monitored. Thecal cell P secretion increased from 27 to 72 h. hCG significantly (P less than 0.05) increased P levels after 36 h compared to controls. E or E + hCG decreased P levels at 36, 48, and 72 h and DHT prevented the hCG-induced increase in P secretion. 3 beta-HSD activity in thecal microsomes increased significantly from 27 to 72 h. hCG had little effect on 3 beta-HSD activity compared with controls from 27 to 36 h, but significantly (P less than 0.05) decreased 3 beta-HSD activity at 48 and 72 h. However, P or P + hCG significantly (P less than 0.05) decreased 3 beta-HSD activity at all times. In addition, E or E + hCG significantly (P less than 0.05) decreased 3 beta-HSD activity at 48 and 72 h. DHT prevented the hCG-induced decrease in 3 beta-HSD activity. In conclusion, porcine thecal secretion of P and microsomal 3 beta-HSD activity increased during 72 h of culture. Paradoxically, the addition of hCG to cultures enhanced media P concentrations but inhibited 3 beta-HSD activity. Further, the addition of E to cultures decreased media concentrations of P while P or E decreased 3 beta-HSD activity. Therefore, paracrine/autocrine effects of locally produced steroids may play a role in modulating thecal cell steroidogenesis.