Age changes in rat testicular capsular and parenchymal delta 13-reductase and 15-hydroxyprostaglandin dehydrogenase activities

Testosterone induction of prostaglandin-endoperoxide synthase 2 expression and prostaglandin F(2alpha) production in hamster Leydig cells

We have previously observed expression of prostaglandin-endoperoxide synthase 2 (PTGS2), the key enzyme in the biosynthesis of prostaglandins (PGs), in reproductively active Syrian hamster Leydig cells, and reported an inhibitory role of PGF(2alpha) on hamster testicular steroidogenesis. In this study, we further investigated PTGS2 expression in hamster Leydig cells during sexual development and photoperiodic gonadal regression. Since PTGS2 is mostly expressed in pubertal and reproductively active adult hamsters with high circulating levels of LH and androgens, we studied the role of these hormones in the regulation/maintenance of testicular PTGS2/PGF(2alpha). In active hamster Leydig cells, LH/hCG and testosterone induced PTGS2 and PGF(2alpha) production, and their actions were abolished by the antiandrogen bicalutamide (Bi). These results indicate that LH does not exert a direct effect on PG synthesis. Testosterone also stimulated phosphorylation of the mitogen-activated protein kinase isoforms 3/1 (MAPK3/1) within minutes and hours, but the testosterone metabolite dihydrotestosterone had no effect on PTGS2 and MAPK3/1. Because Bi and U0126, an inhibitor of the MAP kinase kinases 1 and 2 (MAP2K1/2), abolished testosterone actions on MAPK3/1 and PTGS2, our studies suggest that testosterone directly induces PTGS2/PGF(2alpha) in hamster Leydig cells via androgen receptors and a non-classical mechanism that involves MAPK3/1 activation. Since PGF(2alpha) inhibits testosterone production, it might imply the existence of a regulatory loop that is setting a brake on steroidogenesis. Thus, the androgen environment might be crucial for the regulation of testicular PG production at least during sexual development and photoperiodic variations in hamsters.

Prostaglandin dehydrogenase activity of rat and rabbit testicular tissues and accessory glands before and after castration

Rat reproductive tissues contained both 15-hydroxy-prostaglandin dehydrogenase (PGDH) and delta 13-reductase activities, while rabbit tissues exhibited only PGDH activity. In the rat, delta 13-reductase activity was absent in those tissues that had a high specific activity of PGDH and was present in those tissues with a low specific activity. Total specific activity of PGDH was greatest in the testicular capsule, whereas total activity was greatest in the testicular parenchyma of both species. Total PGDH activity was highest in rat seminal vesicles, where it was second only to the testicular parenchyma. Castration significantly increased PGDH activity of the epididymis, prostate, and seminal vesicles of rats, while delta 13-reductase activity disappeared from those tissues. The specific activity of PGDH was greater in the rat than in the rabbit, except for the testicular parenchyma of the rabbit. The greater PGDH activity in rat testicular capsules, compared to those of the rabbit, correlated well with diminished contractility of the rat capsule. PGDH activity of the interstitial cells correlated well with the role of prostaglandins in androgen synthesis.

Indomethacin decreases both luteinizing hormone binding and fluidity of testicular microsomal membranes in rat

The objective of these studies was to examine the effects of in vivo treatment with indomethacin, a prostaglandin synthesis inhibitor, on luteinizing hormone receptors and fluidity in microsomal membrane preparations of rat testis. Adult male rats were treated with vehicle or either of two doses of indomethacin (3.8 micrograms/g body weight or 7.5 micrograms/g body weight) every 8 h for 1, 2 and 3 days. Indomethacin treatment decreased human luteinizing hormone (hLH) binding in rat testis in a time-dependent fashion. The lower dose of indomethacin decreased hLH binding by 19%, 35% and 50%, respectively, after 1, 2 and 3 days of treatment. The higher dose of indomethacin decreased hLH binding at these respective times by 21%, 44% and 56%. Scatchard analysis of the hLH binding of testicular membrane preparations indicated that indomethacin treatment decreased the number of hLH binding sites rather than the apparent affinity constant. Testicular membrane fluidity was estimated by a fluorescence polarization technique. The effects of indomethacin on apparent fluidity of microsomal membrane paralleled that of LH binding. The values of apparent microviscosity, inversely related to the fluidity, also increased in a time-dependent fashion. These simultaneous effects of indomethacin on testicular LH binding and fluidity suggest that these phenomena are interrelated and that prostaglandins are involved in the maintenance of LH receptors in vivo.