Effects of Dietary Protein on Glomerular Eicosanoid Production in Rats with Bilateral Ureteral Obstruction

Abstract

Abstract

Greater protein intake increases glomerular elcosanold production in rats. Bilateral ureteral obstruction (BUO) also enhances glomerular elcosanold production in experimental animals. To examine the effects of dietary protein intake on glomerular elcosanold production in ureteral obstruction, we measured the in vitro production of the vasodilatory prostaglandins, PGE₂, and 6-keto PGF_1α, and the vasoconstrictor, TxB₂, and the mass of cyclooxygenase in glomeruli of sham-operated control (SOC) rats and rats with BUO of 24 hr duration fed a low- (6% casein) or a high- (40% casein) protein diet for approximately 4 weeks. The animals were pretreated or not with the anglotensin converting enzyme inhibitor, enalaprilat, prior to sham-operation or ureteral obstruction. Glomeruli from SOC rats fed a high-protein diet produced significantly greater amounts of PGE₂, 6-keto PGF_1α, and TxB₂, and had substantially increased mass of cyclooxygenase when compared with glomerull from SOC rats fed a low-protein diet. Pretreatment of animals with enalaprilat prior to sham operation prevented the increase in glomerular eicosanoid production and cyclooxygenase content in SOC rats fed a high-protein diet and the levels observed were similar to those in SOC rats fed a low-protein diet. Both elcosanoid production and cyclooxygenase mass were further increased in glomeruli from rats with BUO fed a high-protein diet when compared with glomeruli of SOC rats fed the same diet. The increased levels of these measurements in BUO rats fed a high-protein diet fell markedly when the rats were pretreated with enalaprilat in vivo. The values were essentially comparable to those of SOC rats fed a low-protein diet. By contrast, there was no substantial increase in the production of PGE₂, 6-keto PGF_1α) and TxB₂ and in the mass of cyclooxygenase in glomeruli of BUO versus SOC rats fed a low-protein diet.