The overall objective is to determine what are the factors in portal venous blood that influence hepatic structure, function, and the capacity for regeneration. Also under study is the way in which such factors work, and how the presumably multiple "hepatotrophic" factors interact. The goals during the current year in the experimental laboratory are to determine the effect of extirpation of different splanchnic organs upon the intact liver or upon the liver remnant after 44% and 72% hepatic resection. In some experiments all of the nonhepatic splanchnic viscera will be removed, in others all will be removed except the pancreas and in a final group the pancreas alone will be excised. The effects of these procedures upon hepatocyte structure and mitotic rate will be measured in intact livers and in livers submitted to 44% and 72% hepatectomy. In addition, responsiveness of adenyl cyclase to glucagon stimulation and changes in cyclic AMP in hepatocytes under the foregoing conditions will be measured.