The overall objective of this research is to elucidate specific areas of the metabolism and transport of cholesterol by the intestinal tract. These include the following: 1) To delineate the nature of the mucosal cell "barrier" to the absorption of cholesterol and other sterols. This involves in vitro studies with intestinal segments. 2) To determine the mechanism of activation of mucosal sterol ester hydrolase and clarify its role in the transport of absorbed or synthesized cholesterol in the intestine. These studies are conducted with the purified enzyme and its antibodies. 3) To elucidate the mechanism(s) of sex hormone control of cholesterol absorption and transport. This includes studies on effects of sex hormones per se, and differential effects of transport inhibitors in animals of both sexes.