The major objective of the proposed studies is to define the hormonal (catecholamine) influence on cardiac prostaglandin synthesis. Specifically, studies will be performed to elucidate the mechanism of beta adrenergic receptor stimulated cardiac prostaglandin synthesis in terms of: 1) contribution of extra- and intracellular Ca++ and calmodulin by examining the effects of a) alterations in extracellular Ca++, b) Ca++ channel blockers and intracellular Ca++ antagonists and c) calmodulin inhibitors; 2) role of cyclic AMP by examining the consequence of alterations in the activity of adenylate cyclase-cyclic AMP system by using an adenylate cyclase activator (forskolin) and inhibitor (2,5 dideoxyadenosine), phosphodiesterase inhibitor (IBMX and 8-bromo-and dibutyryl cyclic AMP; 3) role of phospholipid methylation by using inhibitors of transmethylation (3-deazaadenosine and L-homocysteine thiolactane); 4) participation of polyamine synthesis by studying the effects of an ornithine decarboxylase inhibitor (alpha-difluromethylornithine) and exogenous polyamines (putrescine, spermine, spermidine) and 5) contribution of phospholipase A2 and/or C in the release of arachidonic acid for prostaglandin synthesis by a) examining the actions of lipase inhibitors (mepacrine, beta-bromophenyacyl bromide, dexamethasone) and b) determining the distribution of (C14)arachidonic acid in various lipid fractions in hearts with and without hormone challenge. Alterations in prostaglandin output elicited by catecholamines from the heart during various interventions will be related to changes in mechanical function of the heart. All studies will be conducted in the isolated rabbit heart. Prostaglandin output from the heart will be determined by radioimmunoassay. The content of various lipid fractions will be determined by TLC arid colorimetric procedures and distribution of (C14)arachidonic acid in various lipid fractions by TLC and liquid scintillation counting. Information derived from these studies should further our understanding of the mechanisms regulating cardiac actions of catecholamines on prostaglandin synthesis and mechanical function of the heart and contribute to the development of a rational approach for the diagnosis, prevention and treatment of cardiovascular disease.
