RENAL HEMODYNAMICS AND BLOOD-FLOW AUTOREGULATION DURING ACUTE CYCLOOXYGENASE INHIBITION IN MALE-RATS

After the acute inhibition of prostanoid synthesis, adjustments of ren al hemodynamics may not be characterized immediately. Therefore, time- related effects of indomethacin on hemodynamics and renal blood flow ( RBF) autoregulation were studied in anesthetized euvolemic male rats i njected intravenously with vehicle, indomethacin (3, 4, or 5 mg/kg bod y wt), or medofenamate (4 or 5 mg/kg body wt). Hemodynamics and RBF au toregulation were not influenced by vehicle injection, nor by time (n = 6). In contrast. mean arterial pressure (MAP) decreased significantl y from 117 +/- 4 to 103 +/- 3 mmHg, and RBF progressively and signific antly increased from 8.00 +/- 0.34 to 9.17 +/- 0.50 ml/min in the 3 mg /kg body wt indomethacin group (n = 8). Treatment with the higher dose s of indomethacin (n = 9) or meclofenamate (n = 6) did not change RBF, while MAP decreased by 15 mmHg. A time-dependent significant enhancem ent of RBF autoregulatory efficiency was found in the drug-treated rat s. Changes in renal function and reductions of prostanoid excretion in urine, of plasma renin activity, or serum aldosterone were similar in the nonsteroidal antiinflammatory drug groups. In conclusion, our fin dings demonstrate important time-related adjustments of renal hemodyna mics in male rats treated with indomethacin, especially with the lower dose (3 mg/kg body wt iv). The factor(s) responsible for the hemodyna mic changes remains unknown.