Mechanisms involved in alpha-adrenergic control of hepatic carbohydrate metabolism will continue to be explored along the following lines: 1. Characterization of the alpha1- and alpha2-adrenergic receptors of liver plasma membranes. 2. Chemical characterization of the putative intracellular messenger of the alpha-adrenergic system. 3. Delineation of the possible role of phosphatidylinositol turnover in alpha-adrenergic effects. 4. Determination of the intracellular organelle(s) from which Ca2 ion is released during alpha-adrenergic stimulation. 5. Characterization of the mechanisms involved in such release. 6. Delineation of the roles of Ca2 ion and calmodulin in the enzyme changes induced by alpha-adrenergic activation.