The purpose of this investigation is to elucidate some of the mechanisms involved in the hormonal, neural, and local metabolic regulation of blood flow through the hepatic microvasculature during conditions of optimal circulation and low flow states (shock and hepatic disease). This will be accomplished by using "in vivo" microscopy concomitant with physiologic, pharmacologic, neurohistochemical, and electron microscopic procedures. The results of these studies should provide an improved understanding of the mechanisms for regulating blood flow through the hepatic sinusoids. This should be helpful in the development of more effective therapy for disturbances of the hepatic circulation that result from circulatory shock or disease.