Effect of acetylsalicylic acid, paracetamol, caffeine and a combination of these substances on the renal prostaglandin E2, 6-keto-prostaglandin F1 alpha, water, creatinine and electrolyte excretion of the rat.

The aim of the study was to investigate the effect of acetylsalicylic acid (CAS 50-78-2, ASA), paracetamol (CAS 103-90-2) and caffeine (CAS 58-08-2) and a combination of these substances on the renal prostaglandin excretion of rats loaded with water. In addition to the effects on the renal excretion of prostaglandin E2 (PGE2) and 6-keto-prostaglandin F1 alpha (6-keto-PGF1 alpha), the effect on the electrolyte, creatinine and water excretion was measured. Even in low doses ASA led to a dose-dependent reduction in the renal PGE2 and 6-keto-PGF1 alpha excretion. In oral doses up to 200 mg/kg paracetamol did not have any effect on the renal prostanoid excretion. In the combination it did not change the effect of ASA on the prostaglandin excretion. Caffeine caused a marked dose-dependent increase in the PGE2 excretion. The effect of caffeine on the renal 6-keto-PGF1 alpha excretion was less marked. In combination with ASA, with and without the addition of paracetamol, caffeine reduced the inhibitory effect of ASA on the excretion of arachidonic acid metabolites. The values for the renal prostaglandin excretion did not show any clear correlation with the other parameters of diuresis.