Villa, Eduardo

Abstract Rapid degradation of prostacyclin (PGI 2 ) inherent to its molecular structure has long been a major limitation in assessing the natriuretic effect of this prostaglandin. The recent availability of the stable PGI 2 analogue iloprost now allows for a comparative study with prostaglandin E 2 (PGE 2 ). In the present study conducted in six anesthetized dogs, the intrarenal effects of two consecutive doses (1 and 4 ng · kg −1 · min −1 ) of PGE 2 on renal blood flow, glomerular filtration rate, and urinary sodium excretion were compared with the effects of two identical doses of iloprost. The selected doses of PGE 2 were those producing a maximal natriuretic and vasodilator response without affecting mean arterial pressure. A washout period was allowed between administration of PGE 2 and iloprost. PGE 2 infusion significantly increased fractional sodium excretion from 0.69±0.1 to 2.79±1.1% and 4.27±1.2%% ( P <.05), respectively. These changes in fractional sodium excretion induced by PGE 2 were associated with significant increases in renal blood flow from 151.1±62 to 185±64.3 and 185.6±64.3 mL/min ( P <.05), respectively; however, no significant alterations were seen in glomerular filtration rate, from 29.5±9.4 to 35.2±12.2 and 32.7±7.8 mL/min (NS), and mean arterial pressure, from 117.6±26 to 113.9±24.1 and 112.3±24.1 mm Hg (NS) during control and PGE 2 infusion. At identical doses, sequential infusion of PGI 2 had no effect on renal blood floww and glomerular filtration rate, producing natriuresis only at the highest dose, a fractional sodium excretion from 0.69±0.1 to 0.8±0.28 mm Hg (NS) and 1.05±0.34% ( P <.05), respectively. In conclusion, the present study confirms that PGE 2 exerts a natriuretic effect during increases in renal blood flow. In contrast, PGI 2 had no hemodynamic effect, and the natriuresis was markedly blunted.