Factors that influence blood flow in skeletal muscle and skin

Abstract

Recently there has been a rapid increase in knowledge about the control of steroidogenesis in the testes. This has come about because of the relatively simple and sensitive methods that are now available for measuring steroids and cAMP and because of the in vitro tissue systems which have been developed. It is now possible to use intact testis tissue and testis separated into interstitial tissue and seminiferous tubules to study the effects of physiological amounts of trophic hormones on cAMP and steroidogenesis. The data obtained indicate that cAMP may be a second messenger of LH on steroidogenesis in the testis because LH specifically stimulates cAMP and steroidogenesis in interstitial tissue and whole testis tissue and the increase in cAMP occurs before the increase in steroidogenesis. In addition dibutyryl cAMP stimulates testosterone production. Not in accordance with cAMP being the second messenger is the finding that low levels of LH stimulate steroidogenesis without there being detectable changes in cAMP levels. FSH on the other hand specifically stimulates cAMP production only in the seminiferous tubules and apparently has no effect on steroidogenesis. Very little is known about the mechanism of cAMP steroidogenic action in the testis. It has yet to be determined if similar mechanisms to those proposed for the adrenal gland and ovary i.e. via protein kinase and protein synthesis also exist in the testis. (94 references.)