Masculinization depends on adequate production of testosterone by the fetal testis within a specific "masculinization programming window." Disorders resulting from subtle deficiencies in this process are common in humans, and environmental exposures/lifestyle could contribute causally because common therapeutic and environmental compounds can affect steroidogenesis. This evidence derives mainly from rodent studies, but because there are major species differences in regulation of steroidogenesis in the fetal testis, this may not always be a guide to potential effects in the human. In addition to direct study of the effects of compounds on steroidogenesis, information also derives from study of masculinization disorders that result from mutations in genes in pathways regulating steroidogenesis. This review addresses this issue by critically reviewing the comparative timing of production and regulation of steroidogenesis in the fetal testis of humans and of rodents and its susceptibility to disruption; where there is limited information for the fetus, evidence from effects on steroidogenesis in the adult testis is considered. There are a number of fundamental regulatory differences between the human and rodent fetal testis, most notably in the importance of paracrine vs. endocrine drives during masculinization such that inactivating LH receptor mutations block masculinization in humans but not in rodents. Other large differences involve the steroidogenic response to estrogens and GnRH analogs and possibly phthalates, whereas for other compounds there may be differences in sensitivity to disruption (ketoconazole). This comparison identifies steroidogenic targets that are either vulnerable (mitochondrial cholesterol transport, CYP11A, CYP17) or not (cholesterol uptake) to chemical interference.

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American black bears, Ursus americanus, are seasonal breeders with a mating season in late spring to early summer. The objectives of this study were to determine whether there are seasonal changes in spermatogenesis and immunolocalization of testicular steroidogenic enzymes, and to correlate these changes with peripheral steroid concentrations. Three captive mature bears were maintained in open cages during the summer season and provided with chambers for denning during the winter. Testicular biopsies and blood samples were obtained from anaesthetized bears on 12 March, 15 June, 12 October and 15 January. Steroidogenic enzymes were immunolocalized using polyclonal antisera raised against bovine adrenal cholesterol side-chain cleavage cytochrome P450 (P450scc), human placental 3 beta-hydroxysteroid dehydrogenase (3 beta HSD), porcine testicular 17 alpha-hydroxylase cytochrome P450 (P450c17) and human placental aromatase cytochrome P450 (P450arom). Spermatogenesis changed seasonally: spermatogonia and degenerating spermatocytes were observed in October; spermatogonia and primary spermatocytes were present in January; spermatogonia, spermatocytes and round spermatids were present in March; and spermatogonia through spermatozoa were present in June. P450scc and P450c17 were immunolocalized in spermatids and Leydig cells in June, whereas in October these enzymes were present only in Leydig cells. 3 beta HSD was localized in Leydig cells in June and October with more intense staining in June. Localization of P450arom changed seasonally: no immunostaining in October; positive immunostaining in Sertoli cells in January; more extensive immunostaining in Sertoli cells, peritubular-myoid cells and round spermatids in March; and strong immunostaining in Sertoli cells and round and elongating spermatids in June. Serum testosterone and oestradiol concentrations changed seasonally: testosterone and oestrogen were low in October and January, slightly higher in March, and high in June. The present study demonstrates that in the black bear seasonal changes in spermatogenesis are accompanied by changes in the immunolocalization of testicular steroidogenic enzymes that are correlated with changes in serum testosterone and oestradiol concentrations. The presence of P450arom in Sertoli cells at the beginning of testicular recrudescence suggests that aromatase and oestrogen may play a role in re-initiating spermatogenesis.

It is established that androgens and unidentified Sertoli cell (SC)-derived factors can influence the development of adult Leydig cells (LC) in rodents, but the mechanisms are unclear. We evaluated adult LC development and function in SC-selective androgen receptor (AR) knockout (SCARKO) and complete AR knockout (ARKO) mice. In controls, LC number increased 26-fold and LC size increased by approximately 2-fold between 12 and 140 d of age. LC number in SCARKOs was normal on d 12, but was reduced by more than 40% at later ages, although LC were larger and contained more lipid droplets and mitochondria than control LC by adulthood. ARKO LC number was reduced by up to 83% at all ages compared with controls, and LC size did not increase beyond d 12. Serum LH and testosterone levels and seminal vesicle weights were comparable in adult SCARKOs and controls, whereas LH levels were elevated 8-fold in ARKOs, although testosterone levels appeared normal. Immunohistochemistry and quantitative PCR for LC-specific markers indicated steroidogenic function per LC was probably increased in SCARKOs and reduced in ARKOs. In SCARKOs, insulin-like factor-3 and estrogen sulfotransferase (EST) mRNA expression were unchanged and increased 3-fold, respectively, compared with controls, whereas the expression of both was reduced more than 90% in ARKOs. Changes in EST expression, coupled with reduced platelet-derived growth factor-A expression, are potential causes of altered LC number and function in SCARKOs. These results show that loss of androgen action on SC has major consequences for LC development, and this could be mediated indirectly via platelet-derived growth factor-A and/or estrogens/EST.

Two distinct genes encode the 93% homologous type 1 (placenta, peripheral tissues) and type 2 (adrenals, gonads) 3␤-hydroxysteroid dehydrogenase/isomerase (3␤-HSD/isomerase) in humans. Mutagenesis studies using the type 1 enzyme have produced the Y154F and K158Q mutant enzymes in the Y ) in the type 1 enzyme. The mutant and wild-type enzymes have been expressed and purified. The K m value of dehydroepiandrosterone is 13-fold greater, and the maximal turnover rate (K cat ) is 2-fold greater for wild-type 2 3␤-HSD compared with the wild-type 1 3␤-HSD activity. The H156Y mutant of the type 1 enzyme has substrate kinetic constants for 3␤-HSD activity that are very similar to those of the wild-type 2 enzyme. Dixon analysis shows that epostane inhibits the 3␤-HSD activity of the wildtype 1 enzyme with 14 -17-fold greater affinity compared with the wild-type 2 and H156Y enzymes. The Y154F and K158Q mutants exhibit no 3␤-HSD activity, have substantial isomerase activity, and utilize substrate with K m values similar to those of wild-type 1 isomerase. The Y269S and K273Q mutants have low, pH-dependent 3␤-HSD activity, exhibit only 5% of the maximal isomerase activity, and utilize the isomerase substrate very poorly. From these studies, a structural basis for the profound differences in the substrate and inhibition kinetics of the wildtype 1 and 2 3␤-HSD, plus a catalytic role for the Tyr 154 and Lys 158 residues in the 3␤-HSD reaction have been identified. These advances in our understanding of the structure/function of human type 1 and 2 3␤-HSD/isomerase may lead to the design of selective inhibitors of the type 1 enzyme not only in placenta to control the onset of labor but also in hormone-sensitive breast, prostate, and choriocarcinoma tumors to slow their growth.

SUMMARYDysregulation of IL-6 synthesis is thought to play a role in the development of a number of age-related conditions, such as rheumatoid arthritis, osteoporosis, atherosclerosis, Alzheimer's disease and B cell malignancies. Recently it has been suggested that the production of IL-6 is in¯uenced by the adrenal hormone dehydroepiandrosterone (DHEA) and its sulphated derivative DHEA-S. In humans we investigated the relationship between DHEA-S, IL-6, IL-6 sR and TGF-b1 in the serum of normal healthy male and female blood donors. Using immunoassay techniques we found that the serum levels of DHEA-S signi®cantly (P 0´0001) decreased with age in both males and females. Furthermore, mean DHEA-S levels in all age groups were signi®cantly (P 0´0001) higher in males. Such correlations were not apparent for IL-6 using a standard assay, but a high sensitivity assay revealed that serum IL-6 was signi®cantly (P 0´0018) positively correlated with age in males only. In addition, serum levels of DHEA-S were signi®cantly (P 0´048) negatively correlated with serum IL-6, again in male subjects only. In contrast, serum IL-6 sR and TGF-b1 levels were not correlated with age in either males or females and were not signi®cantly different between the sexes. However, a signi®cant (P 0´024) negative correlation between DHEA-S and IL-6 sR was found in males. These studies clearly highlight the complex nature of the relationship between these molecules in the ageing process in normal healthy blood donors and demonstrate the need to use high sensitivity assays when measuring IL-6 in apparently healthy individuals under the age of 70 years.

The levels of expression of mRNA species encoding cholesterol side-chain cleavage cytochrome P-450 (P450scc), 17 alpha-hydroxylase cytochrome P450 (P450(17 alpha], aromatase cytochrome P-450 (P-450AROM), and 3 beta-hydroxysteroid dehydrogenase (3 beta HSD) were examined in human follicles and corpora lutea (CL) throughout the menstrual cycle. Tissues were obtained from women undergoing hysterectomy and oophorectomy. The largest follicle or the CL was dissected from the ovary depending on whether the surgery was performed in the follicular or luteal phase. The day of the cycle was determined by onset of last menstrual period and was confirmed by endometrial histology. Total RNA was examined by Northern blot analysis, using as probes specific 32P-labeled cDNA inserts encoding each human enzyme. Early follicles demonstrated detectable mRNA for both P450scc and P450(17 alpha), but not for P450AROM or 3 beta HSD. P450AROM was detectable late in the follicular phase and appeared markedly induced in the CL. 3 beta HSD was detectable only in the CL. Levels of P450(17 alpha) mRNA remained relatively unchanged throughout the cycle, whereas P450scc mRNA levels were greatly increased in the CL. The presence of P450(17 alpha) mRNA in the human CL is of interest, since it is absent from the bovine CL, and this is consistent with the ability of the human, but not the bovine, CL to synthesize 17 alpha-hydroxyprogesterone and estrogens. The fact that P450AROM expression is highest in CL is surprising, since plasma estrogen levels are highest during the late follicular phase of the cycle, and may suggest that CL estrogen biosynthesis is limited by 17 alpha-hydroxylase or 17,20-lyase activities.