Renal effects of prolonged high protein intake and COX2 inhibition on hypertensive rats with altered renal development.

Cyclooxygenase 2 (COX2) is involved in regulating renal hemodynamics after renal ablation. It is also known that high protein intake (HPI) leads to a deterioration of renal function when there is preexisting renal disease and that there are important gender differences in the regulation of renal function. This study tested the hypothesis that the role of COX2 in regulating renal function and the renal hemodynamic effects elicited by HPI are enhanced when nephrogenesis is altered during renal development. It was also expected that the role of COX2 and the effects elicited by HPI are age and sex dependent. Newborn Sprague-Dawley rats were treated with an AT(1) ANG II receptor antagonist during the nephrogenic period (ARAnp). Experiments were performed at 3-4 and 10-11 mo of age. Arterial pressure was elevated (P < 0.05) at both ages and in both sexes of ARAnp-treated rats. Renal COX2 expression was only elevated (P < 0.05) at 10-11 mo of age in both sexes of ARAnp-treated rats. COX2 inhibition induced greater renal vasoconstriction in male and female hypertensive than in normotensive rats at both ages. HPI did not induce glomerular filtration rate (GFR) in the youngest hypertensive rats and in the oldest female hypertensive rats. However, the GFR decreased during HPI (0.63 ± 0.07 to 0.19 ± 0.05 ml/min) in the oldest male hypertensive rats. The HPI-induced increment in proteinuria was greater (P < 0.05) in male (99 ± 22 mg/day) than in female (30 ± 8 mg/day) hypertensive rats. These results show that COX2 plays an important role in the regulation of renal function when renal development is altered and that prolonged HPI can lead to a renal insufficiency in males but not in females with reduced nephron endowment.