Augmentation of diabetes-associated renal hyperfiltration and nitric oxide production by pregnancy in rats

We tested the hypothesis that pregnancy might increase diabetes-associated nitric oxide (NO) production and renal hyperfiltration. Two weeks following i.v. streptozotocin (40 mg/kg), mean arterial pressure (MAP) was not modified by diabetes; glomerular filtration rate (GFR), renal plasma flow (RPF) and filtration fraction (FF) were higher in pregnant than in virgin controls and increased by diabetes to a greater extent in pregnant than in virgin rats. Urinary volume (UV), creatinine, albumin and sodium (UNAV) were significantly increased by diabetes. Diabetes led to an increase in renal, cardiac, aortic and uterine but not in placental NO synthase activities. Infusion of N-G-nitro-L-arginine (L-NA) caused a dose-dependent reduction in GFR, RPF, plasma NO2-/NO3-, UV and UNAV; in general, diabetes increased these effects to a greater extent in pregnant than in virgin rats. L-NA increased MAP in all groups of rats but did not alter FF. Diabetes did not alter responses of thoracic aorta rings to vasoconstrictor effects of phenylephrine and the vasorelaxant effects of sodium nitroprusside but increased endothelium-dependent relaxant effects of acetylcholine. In general the effects of diabetes of 7 days duration were similar to those described above for diabetes of 14 days duration. These data suggest that diabetes-associated renal hyperfiltration and NO production are augmented by pregnancy.