ECDYSONE AS A HYPOCHOLESTEROLEMIC AGENT

It is well-known from the previous findings (Tomkins et al., 1953; Bucher et al., 1959 and 1960) that cholesterol inhibits its own synthesis by a negative feed-back control. Since then, bile salts and their conjugates in the enterohepatic circulation have been shown to be implicated in the regulation of cholesterol synthesis by a double feed-back mechanism, acting either directly by repressing the activity of hydroxymethylglutaryl-CoA reductase [mevalonate : NADP oxidoreductase (acylating CoA); E.N. 1.1.1.34] or indirectly by inhibiting cholesterol catabolism (Beher et al., 1962). More recently the inhibitory effect has been attributed to the presence of hydroxyl groups in these compounds (Fimognari and Rodwell, 1965; Dean and Whitehouse, 1967). The results obtained with steroids which also are cholesterol catabolites are unfortunately less conclusive (Arnold et al., 1967; Noble and Boucek, 1957). The in vivo studies of Boyd (1961) and Horlick; (1965) would support a stimulatory effect of estrogens upon hepatic cholesterogenesis whereas the in vivo studies of TOMKINS et al. (1953); Haksar et al., (1967) and the in vitro studies of Singer et al.(1959), Merola and Arnold (1964); Merola et al. (1968) and Hijwek et al. (1962) would rather support an inhibitory effect. © 1969 Informa UK Ltd All rights reserved: reproduction in whole or part not permitted.