PubMed · 4227783
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A C Brownie, J C Hoschoian. 1967. Testosterone biosynthesis in monkey testis.. https://pubmed.ncbi.nlm.nih.gov/4227783/
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3 beta-Hydroxysteroid dehydrogenase/delta 5-delta 4 isomerase (3 beta-HSD/I) and cytochrome P-450C21 were co-purified from bovine adrenocortical microsomes by an improved method. The 3 beta-HSD/I was successfully incorporated into liposomal membranes in which the enzyme activity was greatly stabilized. Enzymatic activities and kinetic parameters of the 3 beta-HSD/I proteoliposomes were almost the same as those of the solubilized form.
Human cytochrome b5 has a profound effect on the 17,20-lyase activities catalyzed by purified, human cytochrome P450c17. It enhances the conversion of 17 alpha-hydroxypregnenolone to dehydroepiandrosterone by 13-fold and the conversion of 17 alpha-hydroxyprogesterone to androstenedione by at least 10-fold. This latter activity is virtually undetectable in the absence of cytochrome b5. Other activities catalyzed by P450c17 include 17 alpha-hydroxylation of progesterone and pregnenolone and are much less influenced by cytochrome b5. The conversion of pregnenolone to 17 alpha-hydroxypregnenolone is increased by 2-fold, while that of progesterone to 17 alpha-hydroxyprogesterone is unchanged. These studies using purified systems suggest that cytochrome b5 plays a role in regulating the activities of P450c17 to optimize the balance between sex hormone synthesis and glucocorticoid synthesis. In particular, they indicate that in human testes which contains a high b5/P450 ratio, 17 alpha-hydroxyprogesterone can serve as an intermediate in testosterone production, rather than being a dead-end product, or stated another way, because of the relatively high concentration of cytochrome b5 in the human testis, both the delta 4 and the delta 5 steroidogenic pathways can lead to testosterone production.
Progressive ischemia and necrosis of the skin following thermal injury are reduced by postburn administration of the steroid hormone dehydroepiandrosterone (DHEA). Thermally injured animals were provided with a subcutaneous injection of DHEA, or a related species of steroid hormone, at various times after burning. During the 96 hr following administration of the scald burn, tissue necrosis was closely monitored. Subcutaneous administration of DHEA at approximately 1 mg/kg/day achieved optimal protection against the development of progressive dermal ischemia. DHEA, 17 alpha-hydroxy-pregnenelone, 16 alpha-bromo-DHEA, and androstenediol each demonstrated, a similar level of protection. Other forms of steroids, including DHEA sulfate, androstenedione, 17 beta-estradiol, or dihydrotestosterone, exhibited no protective effect under the conditions tested. Additionally, intervention therapy with DHEA could be initiated up to 4 hr, but not 6 hr, after burn without a marked reduction in therapeutic benefit. Examination of the microvasculature of thermally injured dorsal skin suggested that postburn intervention with DHEA, either directly or indirectly, maintained a normal architecture in most of the dermal capillaries and venules within burn-exposed tissue. These findings suggest that systemic intervention therapy of burn patients with DHEA or a similar acting steroid hormone may be useful in preventing the progressive tissue destruction caused by progressive ischemia.