We studied the role of renal prostaglandins in the regulation of glomerular filtration rate (GFR) and renal blood flow (RBF) in the isolated dog kidney. Indomethacin or meclofenamate, 2 mg/kg of body weight, suppressed renal prostaglandin E2 (PGE2) secretion, measured by radioimmunoassay, to zero within 20 minutes; the effect persisted for the duration of the study. When renal arterial pressure (PRA) was maintained at 104 mm Hg both drugs caused a sharp decrease in sodium excretion and RBF with redistribution of flow from inner to outer cortes we examined autoregulation of GFR and RBF over the pressure ranges of 150-100 and 150-75 mm Hg, respectively, after inhibition of PGE2 secretion and under control conditions. deltaGFR/deltaPRA (ml/min per mm Hg) was 0.020 +/- 0.017 in the indomethacin group, 0.152 +/- 0.055 in the meclofenamate group, and 0.086 +/- 0.017 in the control group. The change in GFR for the indomethacin group was significantly less than that for meclofenamate (P less than 0.01) and control groups (P less than 0.025); the latter two groups were not statistically different from each other (P greater than 0.1). There was no significant difference (P greater than 0.1) between the three groups with respect to deltaRBF/deltaPRA, which measured 0.288 +/- 0.046, 0.370 +/- 0.112, and 0.438 +/- 0.123 ml/min per mm Hg in the indomethacin, meclofenamate and control groups, respectively. Renal was lowered from 150 to 75 mm Hg. The observation that inhibition of prostaglandin synthesis promotes a redistribution of RBF from inner to outer cortex suggests that renal prostaglandins may participate in the regulation of medullary blood flow. However, since autoregulation of GFR and RBF remained intact despite inhibition of prostaglandin secretion, these data argue against a role for renal prostaglandins in regulating whole kidney GFR and RBF.