REGULATION OF CHOLESTEROL-METABOLISM IN ADRENAL-CORTEX - COMPARATIVE-STUDIES ON CHOLESTEROL ESTERASE IN HUMAN ADRENAL-GLANDS

We have studied the nature and characteristics of cholesterol esterase (CEase) in human adrenal adenoma and hyperplasia tissues showing Cush ing's syndrome, comparing with those in normal tissue. Each tissue dem onstrated that two pH optima were found at around 4.5 and 8.0. The res ults of a subcellular distribution study show that acid and alkaline C Ease are mainly located in lysosomes and microsomes, respectively. Our previous data suggested that phosphatidylcholine which was sonicated with cholesteryl oleate as a substrate may play a crucial role in the regulation of CEase in rat adrenal. The effect of phosphatidylcholine was therefore investigated in the present study. Acid CEase in normal tissue was increased in a dose-dependent manner by phosphatidylcholine , but not in the adenoma or hyperplasia tissues. None of those tissues showed any enhancement in alkaline CEase activity when phosphatidylch oline was added to the substrates. It is therefore suggested that the mechanism of regulation of CEase among three different kinds of human adrenals may be different from the data for the effect of phosphatidyl choline. Basal activity of acid CEase in adenoma and hyperplasia was s ignificantly higher than that in normal tissue, and also that of alkal ine CEase in hyperplasia tissue was significantly higher than that in normal tissue. Thus it is suggested that such an adrenocortical disord er as Cushing's syndrome due to adenoma and diffuse hyperplasia of the adrenal cortex may possess the nature and characteristics of autonomy of steroidogenesis which seems to be induced by the active metabolism of cholesterol, when compared with normal tissue.