ABSTRACT
A body of evidence suggests that potent diuretics may exert their effects by interfering with renal cAMP turnover. However, the urinary excretion of cAMP accompanying diuretic action does not change consistently in animals. Cyclic AMP excretion rates following the administration of frusemide, piretanide [a new loop diuretic] or placebo were studied in eight normal volunteers. Early elevation of cAMP excretion rate after frusemide was associated with increased creatinine excretion. Considering the cAMP/creatinine ratio the only significant change following administration of diuretics was an increased ratio between 30 and 90 min after piretanide alone. Although this "late" elevation of cAMP excretion may not reflect the basic biochemical action of piretanide it points to minor differences between the sites of action of frusemide and piretanide