The juxtaglomerular apparatus (JGA) is an assemblage of cells known to be the site of formation and secretion of the renal hypertensive material renin and its anatomical arrangement suggests that it functions as an intrinsic renal regulator of hemodynamics and glomerular filtration. Through these actions, the JGA has the potential to affect the levels of arterial blood pressure. This is the basis for the hypothesis that alterations in JGA function may contribute to some types of hypertensive disease. The long-term objective of this project is to understand how the JGA processes hemodynamic, tabular transport, neural, and humoral information to regulate glomerular filtration, blood flow, and renin release. With a few notable exceptions, specific information about the cells of the JGA is derived from structural studies utilizing light and electron microscopy. Progress on the cell biology and biochemistry of this important group of cells has been limited by their relative inaccessability and the small amount of material in each nephron. This proposal seeks support to develop a convenient method for the isolation of granular and macula densa cells and the subsequent growth of these cells in culture. In the first phase we will develop monoclonal antibodies directed against cell surface antigens to be used as bioaffinity reagents to isolate relatively large quantities of renin-containing and macula densa cells from collagenase dispersions of rabbit and dog kidney cortex. With the ability to isolate specific cell types from the JGA we will proceed to a second phase where we will systemically evaluate growth media and substrata conditions in order to develop culture conditions that best support retention of differentiated properties. Culture conditions for granular cells will be established by determining to conditions necessary to observe modulation of renin production by the cells in response to factors that have been previously found to influence renin release in the intact animal. Culture conditions for macula densa cells will be determined by immuno- and histochemical techniques using antigenic or enzymatic markers previously determined in situ. It is anticipated that the use of monoclonal antibodies to isolate granular and macula densa cells, and the growth of these cells in culture will provide an important model system with which to investigate stimulus-secretion coupling, cyclic nucleotide metabolism, and receptor modulation and thereby advance our understanding of the intrinsic renal regulation of hemodynamics and renin release.
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