The delta 5-3 beta-hydroxy steroid acyl transferase activities in tissues of the male rat and sheep.
Pregnenolone and dehydroepiandrosterone and their sulphate and fatty acid ester derivatives are concentrated in the mammalian brain, as compared to the peripheral organs. Although biological functions have been postulated for the free steroid and sulphate conjugates, the role of steroid fatty acid esters in the central nervous system (CNS) has yet to be established. A comparison of the esterifying capacities of brain and peripheral organs of the male rat and sheep is made here. The male rat brain was found to possess a higher esterifying capacity than all other tissues examined, with 5.32 +/- 2.46 pmol dehydroepiandrosterone fatty acid esters synthesized/mg protein/h and 1.89 +/- 0.42 pmol pregnenolone fatty acid esters synthesized/mg protein/h. Sheep adrenal and sheep liver homogenates were found to have higher esterifying capacities than sheep brain. Within the brain of both species. delta 5-3 beta-hydroxy steroid acyl transferase enzyme(s) were concentrated in the microsomal fraction. The addition of a lecithin:cholesterol acyl transferase inhibitor to incubation assays resulted in a loss in enzyme activity. This effect was more significant in sheep brain microsomes than rat brain microsomes. It is likely that lecithin:cholesterol acyl transferase is more active in the sheep brain than the rat brain. Results from this study indicate that the steroid acyl transferase enzymes that are active in the mammalian brain are substrate specific.
Smith
A J
AJ
School of Biological and Chemical Sciences, Deakin University, Geelong, Victoria, Australia.
Watson
T G
TG
D000217:Acyltransferases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D000818:Animals; D001921:Brain / Q000201:enzymology; D003687:Dehydroepiandrosterone / Q000378:metabolism; D004228:Dithionitrobenzoic Acid / Q000494:pharmacology; D006914:Hydroxysteroids / Q000378:metabolism*; D008297:Male; D051381:Rats; D017207:Rats, Sprague-Dawley; D012756:Sheep
D006914:Hydroxysteroids; D003687:Dehydroepiandrosterone; D004228:Dithionitrobenzoic Acid; D000217:Acyltransferases