The overall goal of this proposal is to investigate the role of inducible forms of nitric oxide in the expression of salt-mediated hypertension in the Dahl/Rapp genetic rat model. The author has accumulated a significant amount of experimental evidences showing that vascular smooth muscle isoform of inducible NOS (NOS2b) of S rat contains a single point of mutation that results in an amino acid substitution at position 714. Such a mutation induced a decrease in the affinity of the enzyme for L-arginine as compared to wild type NOS2b which is responsible for determining salt-sensitive hypertension. The proposal has two major objectives. The first objective is to determine to role of NOS2b gene defect and determining the abnormal function of the enzyme in the production of hypertension in the rat. These goals are accomplished by expressing the wild type NOS2b and the S714P mutant in COS-7 cells to measure Km and determining whether the serine at this position is phosphorylated; examining eight different inbred strains of rat for the S714P mutation using restriction fragment length polymorphism (RFLP) analysis; determining whether the NOS2b RFLP cosegregates with hypertension in an F2 cross between S and R rats; and developing congenic rat strains that posses the NOS2b, S714P mutation and derived from S rats crossed with WKY rats in order to understand the contribution of this mutation to the phenotype of salt-sensitive hypertension and hypertensive nephrosclerosis in vivo. The second long term objective is to determine the manner in which the effect of dietary salt affects steady-state mRNA and protein levels of NOS2b as well as NOS1 and NOS3. These goals also include experiments to examine the mechanism of transport of L-arginine into the smooth muscle cells and determine if this transport is altered in S rats. The proposal also contains studies to determine the mechanism of renal damage in Dahl/Rapp rats. The author has produced evidences indicating that extracellular matrix overproduction in small arterioles and glomerular mesangium is associated with the progressive renal disease in these rats. In this line, the studies aim at determining the role of a defective NO production along with an abnormal responsive angiotensin II on the formation of fibrogenic growth factor.
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