Prostaglandin H2-thromboxane A2 and renal functions in the Lyon hypertensive rat

The influence of renal perfusion pressure (RPP) on renal functions was studied in anesthetized 8-wk-old Lyon hypertensive (LH) and normotensive (LN) rats before and after a specific blockade of prostaglandin (PG) H2-thromboxane (Tx) A2 receptors using GR-32191B. The nervous and hormonal influences on the kidneys were controlled by renal denervation, adrenalectomy, and an infusion of norepinephrine, aldosterone, hydrocortisone, and vasopressin. With the use of inflatable cuffs, RPP was varied from 100 to 125 and then to 150 mmHg. In control conditions, the renal blood flow (RBF) and glomerular filtration rate (GFR) were independent of RPP in both strains. LH kidneys differed from LN controls by an increased preglomerular vasoconstriction as indicated by a similar decrease in RBF and GFR. Moreover, the pressure-natriuresis curve was blunted in LH compared with LN kidneys. GR-32191B did not affect the renal function of LN rats. In LH kidneys, it normalized RBF and renal vascular resistance and improved GFR, whereas it had no effect on the pressure-natriuretic relationship. It is concluded that the elevated preglomerular vascular resistance that characterizes LH rats is dependent on an overstimulation of PGH2-TxA2 receptors whereas these latter are not involved in the control of pressure-natriuresis.