Up-regulation of renal prostaglandin receptors in genetic salt-dependent hypertension.

Development of hypertension in Dahl salt-sensitive rats (DS) is accompanied by reduced renomedullary prostaglandin synthesis, which may be responsible for their lower natriuretic capacity. To examine the changes in renomedullary prostaglandin E2 synthesis, the effects of high (8.0%) and normal (0.6%) NaCl diets were examined in DS and in Dahl salt-resistant rats (DR). In response to an 8.0% NaCl diet, the number of prostaglandin E2 receptors in the renal outer medulla of DR increased (2.97 +/- 0.2 vs 2.18 +/- 0.2 pmol/mg on 0.6% NaCl diet) while no change was noted in their affinities (Kd, 9.5 +/- 0.2 vs 9.4 +/- 0.3 nM). Receptor number and affinity in the renal cortex, inner medulla, and liver of DR were not affected. In contrast, renomedullary receptors of DS had a lower affinity than those of age-matched DR (Kd, 13.9 +/- 0.2 nM on 0.6% NaCl diet and 14.0 +/- 0.3 nM on 8.0% NaCl diet) and did not increase in number after a high salt diet. This apparent inability of DS to modulate prostaglandin receptors may contribute to their susceptibility to salt-induced hypertension.