Effect of pregnancy on plasma renin activity and glomerular synthesis of prostaglandins and thromboxane in rats.

Normal pregnancy in women and rats is characterized by an increased glomerular filtration rate. Because prostaglandin glomerular synthesis has been reported to be increased in 2 other circumstances with glomerular hyperfiltration (streptozotocin-induced diabetes and high protein dietary intake in Heymann nephrilis), we studied prostaglandin biosynthesis in glomeruli obtained from pregnant Wistar rats in comparison with non pregnant rats during the estrus cycle. Comparatively to the 3 first phases of the cycle, and wether or not arachidonic acid was present, PGE2 and PGF2 alpha production rates were found significantly higher in diestrus 2 (2-3 fold increase for both) at 15 days of pregnancy (2 fold increase for PGE2, 5-6 fold increase for PGF2 alpha) and at 21 days of pregnancy (5-6 fold increase for both). On the other hand synthesis of TXB2 was not increased during pregnancy nor during diestrus 2. Plasma renin activity (PRA) was increased during pregnancy. It is concluded that in presence of increased PRA, the increased synthesis of PGE2 may be the hormonal factor explaining, at least in part, the hemodynamic mechanism of glomerular hyperfiltration which has been previously described by micropuncture techniques and characterized by increased renal plasma flow, increased glomerular filtration pressure and decreased ultrafiltration coefficient.