MEDULLARY CYCLOOXYGENASE PRODUCTS AND RENAL DISEASE

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It is now clear the progression of renal disease involves not only the glomerulus, but also the tubulointerstitial region. While many peptide growth factors, cytokines, and vasoactive hormones have been postulated to play an important role in the pathogenesis of progressive nephron destruction, there is potentially a central role for arachidonate products of cyclooxygenase. Because the collecting duct is both a major site for renal cyclooxygenase and prostaglandin synthesis and because numerous experimental models of renal injury have been associated with not only increased glomerular, but also urinary cyclooxygenase products, it would appear critical to investigate the role of collecting duct prostaglandin formation in a relevant model of progressive renal failure. This proposal is to elucidate those factors causing renal prostaglandin synthesis to increase after three-quarters nephrectomy in the rabbit. Studies will focus on the rabbit since monoclonal antibodies recently developed in our laboratory against the collecting duct of this species will allow biochemical characterization of collecting duct cells harvested post sub- total nephrectomy. Using both freshly immunodissected cells as well as cells placed in primary culture, we will examine prostaglandin synthesis, measure cyclooxygenase levels using immunoprecipitation, and cyclooxygenase message using norther blot analysis. We will also determine the effects of sub-total nephrectomy on the expression of P21-ras and P35 proteins that localize to the collecting duct and appear to critically interact with the process of cyclooxygenase product formation. These studies will be extended to examine the effects of increased prostaglandin levels or inhibition of endogenous prostaglandin synthesis on extracellular matrix formation by cultured medullary collecting duct cells and renal medullary interstitial cells. Finally, the effects of prostaglandins and their analogues on growth of cultured collecting duct and renal medullary interstitial cells will be determined. It is the goal of these studies to characterize for the first time the role of the collecting duct in generating prostaglandins after renal injury and the significance of this prostaglandin generation as it relates to functional and structural changes in the renal medulla. This information should open up new avenues for investigation of the progression of renal disease.