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In order to promote better understanding of the physiological roles of prostaglandin F(2alpha) in the mouse testis, we investigated the protein expression and the cellular localization of the enzymes cyclooxygenase and prostaglandin F synthase that are essential for the production of prostaglandin F(2alpha), and the binding site, which is the prostaglandin F(2alpha )receptor (FP). Western blot exhibited the expression of FP protein in wild type mouse testis, and that of prostaglandin F synthase and cyclooxygenase-1 proteins in the both of wild type mouse and FP-deficient mouse testes. The expression of prostaglandin F synthase and cyclooxygenase-1 were detected intensely in Leydig cell-rich fraction, and that of FP was detected equally in Leydig cell-rich fraction and the other fraction. Immunohistochemistry for cyclooxygenase-1 and prostaglandin F synthase demonstrated their co-localization in mouse Leydig cells. Histochemistry for FP demonstrated the localization in Leydig cells and in spermatids of seminiferous tubules. Double histochemical staining confirmed the co-localization of cyclooxygenase-1, prostaglandin F synthase and FP in the Leydig cells. These findings indicate that prostaglandin F(2alpha) may have an effect on the functions of Leyding cells in an autocrine fashion. It implies that prostaglandin F synthase and FP are involved in the control of testosterone release from Leydig cells and in spermatogenesis via the local pathway and the hypothalamo-hypophysial-testis pathway, and affect the testicular function.

Steroid 5alpha-reductase in the rat adrenal gland is supposed to play a role in the catabolism of adrenal steroids. We showed immunohistochemically the cellular and subcellular localization of 5alpha-reductase in the rat adrenal gland, using a polyclonal antibody against 5alpha-reductase rat type 1. In the adrenal cortex, positive immunoreaction was found in the cells of the zonae fasciculata and reticularis but was absent in those of the zona glomerulosa. The positive staining was restricted to the cytoplasm but not to the nucleus, Golgi complexes or mitochondria. The staining intensity showed a marked change depending on the steroidal milieu. Gonadectomy for 6 weeks increased the immunoreaction, regardless of the sex. Testosterone replacement for the last 2 weeks considerably reduced the immunoreaction in 6-week-castrated males, and estradiol supplement for the last 2 weeks also resulted in the marked reduction of immunostaining in 6-week-gonadectomized females. In the adrenal medulla, the immunoreaction was localized in the supporting cells and the Schwann cells but not in the chromaffin cells. In these cells, the immunoreaction was not affected by steroidal treatments. These findings suggest that the expression of 5alpha-reductase in the rat adrenal cortex is regulated by sex hormones from the gonads, and the enzyme may participate in the conversion of adrenal steroids depending on the steroidal environment, although the functional significance of the enzyme in the adrenal medulla remains unclarified.

The localization of 5 alpha-reductase was immunohistochemically studied in the anterior pituitary of male rats, using a polyclonal antibody against 5 alpha-reductase rat type 1. The immunoreactive cells were concentrated in the central region and on the border of the intermediate lobe in the anterior pituitary, but not in the intermediate or posterior lobe. The immunoreaction was located mostly in the cytoplasm and occasionally in the cell nuclei. The immunoreactive cells showed alterations in size and number and in the intensity of the immunoreaction after gonadectomy. One week after castration, the cells became larger and the immunoreactivity increased. Two weeks after castration, the number of immunoreactive cells increased. Double immunostaining using anti-luteinizing hormone beta-subunit or anti-follicle stimulating hormone beta-subunit antibody revealed that most of the cells containing 5 alpha-reductase were gonadotrophs. Electron microscopically, the immunoreactive cells showed lamelliform rough endoplasmic reticulum and a depletion of secretory granules 1 week after castration. One week later, the rough endoplasmic reticulum was developed and dilated and the number of secretory granules increased. These results suggest that 5 alpha-reductase is located in the gonadotrophs of rat anterior pituitary and that it is involved in the feedback regulation of gonadotropin secretion by androgens.

We immunohistochemically studied the localization of 5 alpha-reductase type 1 in combination with androgen receptor (AR) expression in individual lobes of the prostates of intact and castrated rats. In the normal rat prostate, 5 alpha-reductase was localized in the cytoplasm of most epithelial cells in the ventral, dorsal, and lateral type 1 (L1) lobes. Epithelial cells of lateral type 2 (L2) lobes were negative for 5 alpha-reductase. AR was present in the nuclei of all epithelial and stromal cells throughout the prostate. The number of 5 alpha-reductase-immunoreactive cells rapidly decreased in the ventral and L1 lobes after castration, whereas many positive cells remained in the dorsal lobe even at 4 weeks after castration. AR immunostaining was lost in the ventral, dorsal, and L1 lobes at 1 week after castration, but remained in the L2 lobe of 4-week-castrated rats. Electron microscopic immunocytochemistry showed that 5 alpha-reductase was exclusively localized in the rough endoplasmic reticulum membranes and that there were no distinct structural differences between the positively and negatively stained epithelial cells. These findings suggested that the expression of 5 alpha-reductase type 1 in the epithelial cell is heterogeneous within and among the individual lobes of the rat prostate, and does not correspond to AR expression.