KALLIKREIN-KININ SYSTEM IN HYPERTENSION

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The objective is to determine whether tissue kallikreins contribute to the pathology of genetic forms of hypertension in animal models, and ultimately, in man. Important advances in knowledge about tissue kallikreins, their gene families, synthesis and regulation, localization and functional responsibilities, and abnormality in hypertensive states were made over the last five years. The role of tissue kallikreins and their kinin products in renal and intestinal ion and water transport is being revealed, especially in regard to calcium-dependent electrogenic chloride secretion and ADH-stimulated water flow. Components of tissue kallikrein-kinin system(s) are present in the brain and show responses to stimuli important to cardiovascular homeostasis. The demonstration of kallikrein-like enzyme(s) in the vascular wall presents a new opportunity for study of a system suggested to have a role in regulation of vascular resistance. We will use new tools to explore regulation, levels of activity, and roles of tissue kallikreins and their products in the above-mentioned sites in spontaneously hypertensive or Dahl rats. They include: kallikrein mRNA, synthesis rate, zymogen, and active enzyme measurements; the ability to develop and/or maintain primary cell cultures which either contain or are responsive to kallikrein system components; the ability to measure other system components (e.g., kinins, kininogen, a new tissue kallikrein binding protein) or biophysical and biochemical responses to such components (e.g., ion fluxes, channel behavior via patch clamping, eicosanoid synthesis or phosphoinositide turnover); monoclonal antibodies to tissue kallikreins which inhibit or stimulate the enzyme; and kinin receptor blockers. Our specific aims are: 1) to compare tissue kallikrein systems in genetic hypertensive models and their controls; 2) to further explain the roles of tissue kallikreins and kinins in membrane transporting events which relate to cardiovascular homeostasis; 3) to determine whether tissue kallikrein systems contribute causally to genetic forms of hypertensive disease; 4) to pursue these objectives in concert with collaborators who provide different perspectives through work on kallikrein gene expression and enzyme responsibilities, and the role of kallikreins in diabetic renal function.