Our hypothesis is that PGH2/TxA2 and isoprostanes (e.g., 8-iso- PGF2alpha), that are formed largely by oxygen radical (02) attack on arachidonate, act via specific TP receptors (TP-R) to coordinate the renal, vascular, and CNS pathways that regulate BP, renal function, tubuloglomerular feedback (TGF), AVP release, and thirst during physiologic alterations in Ang II or salt intake and specific forms of hypertension. Our preliminary results using a membrane-permeable SOD mimetic (tempol) show that 02- is a potent NO- and TP-R-dependent vasoconstrictor in the normal, and especially in the hypertensive kidney, where 02 coordinates signalling between the macula densa and the afferent arteriole. Therefore, Specific Aim 1 will investigate the generation of 02 - from measurements of 8-iso-PGF2alpha, and its actions on BP, renal hemodynamics, TGF, and isolated afferent arteriole in models of Ang II and salt-dependent hypertension. We find that, whereas in the kidney, isolated glomeruli, and brain stem TP receptor mRNA abundance is enhanced during salt loading by suppression of Ang II action at AT, receptors, there are entirely different patterns of transcriptional regulation of TxA2-S gene products by salt. Therefore, Specific Aim 2 will dissociate the effects of Ang II from salt intake on gene transcription for TxA2-S and TP receptors in kidney and brain. We showed that TP receptors regulate TGF. We now find high levels of 8-iso-PGF2alpha in tubular fluid. Therefore, Specific Aim 3 will investigate intrarenal 8-iso-PGF2alpha generation and tubular fluid delivery and its role in regulation of TGF during changes in salt intake or Ang II. We located mRNA for TP receptors in brain, neuronal, and astroglial cells. We now find that icv injection of a TP receptor antagonist blocks icv Ang II-stimulated drinking, AVP release, and BP and reduces BP in 2K,1C and Ang II-infused but not DOCA/salt rats. Therefore, Specific Aim 4 will use in situ hybridization to locate central sites of TP-R and TxA2-S mRNA expression. Antagonists will be injected icv to investigate the role of TP-R and TxA2-S in the pressor, dipsogenic, and fluid-retaining actions of central Ang II and in Ang II- dependent and renovascular hypertension. We propose conscious animal studies, assessment of JGA transmission using micropuncture and microperfusion, direct studies on the isolated arteriole, and functional studies of CNS with molecular biology of mRNA expression to address the integrative role of TP-R in the kidney and brain in normal physiology and models of hypertension.
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