Reduction of the effects of diuretics or sodium chloride loading in the conscious rat by inhibitors of prostaglandin synthesis

In conscious rats pretreatment with indomethacin or flurbiprofen, two chemically unrelated inhibitors of prostaglandin synthesis, reduced urine volume and sodium excretion induced by four diuretics, acetazolamide, amiloride, bendrofluazide and frusemide, or oral sodium chloride loads. The maximum reduction in sodium excretion was limited to approximately 2 mmol/kg Na⁺ even when sodium excretion was greatly increased. In contrast these inhibitors did not appreciably affect potassium excretion. These results indicate that part of the natriuretic response in the rat to highly and moderately efficacious diuretics and to sodium chloride loading is modified by prostaglandins. We suggest that the lack of effects on potassium excretion indicate that the collecting tubule is the probable site of action.