During the pathogenesis of hypertension and related disorders involving the vascular smooth muscle system there are changes in the state of differentiation of the arterial wall cells which promptly are reflected in changes in gene expression. The objectives of this proposal are: 1) to isolate and characterize rat cDNA clones encoding smooth muscle Alpha-tropomyosin (Alpha-TM), Beta-tropomyosin (Beta-TM), Alpha- and Gamma-actin and myosin light chain (MLC); 2) to utilize the cDNA clones isolated in objective 1 in order to assess their tissue-specific distribution and existence of potential isoforms in different smooth muscle tissues; 3) to study the possible modulation of their expression in different smooth muscle tissues during the onset and course of hypertension in experimental animal models. Expression of tissue-specific isopreteins (outlined in aims 2 and 3) will also be addressed by organ culture of smooth muscle tissues followed by two-dimensional gel electrophoresis analysis of the synthesized proteins; 4) to isolate and characterize the genes corresponding to cDNA clones mentioned in objective 1; 5) to assess the putative regulatory regions (enhancers or enhancer-like elements) involved in the regulation of expression of the smooth muscle specific genes. The isolation, characterization and gene expression studies on the smooth muscle specific genes will be done by established recombinant DNA techniques, (including cDNA cloning in recombinant expression vectors), currently in use in our laboratory. Approximately one quarter of the U.S. population is afflicted with or will develop hypertension. Nevertheless, the genetic contribution towards the genesis of hypertension is completely unknown at the present time. The findings of the proposed research will establish the basis for the understanding, at the molecular genetic level, of some of the intrinsic factors within the vascular smooth muscle cell which may contribute to the pathogenesis of hypertension. The experimental animal studies can be extended in the future to look at hypertensive patients, although these studies are beyond the scope of the current proposal.