Hydroperoxy eicosatetraenoic acids (HPETEs), or oxygen radicals formed by reduction of HPETEs, may influence renal vascular resistance (RVR) and renin release (RR) through direct actions on the effector cells as well as through indirect effects involving inhibition of PGI2 synthetase.
The aim of this proposal is to determine which HPETEs are formed by renal lipoxygenase activity and to clarify the role of various HPETEs (15-, 12- and 5-HPETE) on RVR and RR using several in vitro systems including isolated perfused kidneys, isolated glomeruli and juxtaglomerular cells (JGC) in tissue culture. Initial efforts will be directed towards characterization of the concentration and time-dependence of the renal effects of HPETE and comparison with corresponding hydroxy acids. In analyzing the pattern of arachidonic acid (AA) metabolism by renal tissue, the project will rely heavily on HPLC and GC-MS analyses for separation and identification of specific lipoxygenase products involved in modulation of RVR and RR. The HPETEs infused into isolated kidneys will be radiolabeled so that functional changes can be interpreted in terms of simultaneous variations in the profile of radioactive products appearing in the venous and urinary effluents. Radioconversion studies of AA metabolism will be undertaken, in conjunction with studies of RR, using a superfusion system employing isolated glomeruli enriched in arteriolar attachments. These radioconversion studies will include quantification of the extent of conversion of PGI2 to an active metabolite, 6-keto PGE1. By comparing the profile of AA metabolism to results obtained with glomeruli devoid of arteriolar attachments, as well as to the pattern in intact and de-endothelialized renal arterial segments and cultured JGC, it will be possible to reconstruct which mediators of RR are present in the microenvironment of JGC. Isolated superfused glomeruli will also be used to evaluate the hypothesis that RR may be controlled via a reciprocal interaction between PGI2 and HPETEs. Parallel studies will be carried out with the various in vitro models to determine the influence of mannitol and other free radical scavengers on HPETE responses. In later stages of the project, eicosanoid-dependent RR will be studied as it relates to the pathogenesis of a salt-dependent form of hypertension. Perfused kidneys and glomeruli from salt-sensitive and salt-resistant Dahl rats will be examined for possible strain differences in sensitivity to HPETEs as regards effects on RR and RVR. The influence of scavengers of oxygen radicals will be tested as part of efforts to evaluate the hypothesis that the """"""""hypo-functional"""""""" RR mechanism in hypertension results from a deficit of cellular protective mechanisms for scavenging free radicals.
| Stier Jr, C T; Roberts 2nd, L J; Wong, P Y (1987) Renal response to 9 alpha, 11 beta-prostaglandin F2 in the rat. J Pharmacol Exp Ther 243:487-91 |
