Dopamine, apomorphine, isoproterenol and norepinephrine all increased the concentration of adenosine 3′,5′- monophosphate in the rat kidney particulate preparation, which was composed of tubules, glomeruli and blood vessels. The concentrations of dopamine, apomorphine, isoproterenol and norepinephrine causing a half-maximal increase were 50, 83, 0.1 and 10 μM, respectively. The α-blocker, phentolamine, at a concentration as high as 1 mM, did not significantly reduce the effect of these drugs on the adenosine 3′,5′-monophosphate concentration. The β-blocker, propranolol (50μM), blocked the effect of isoproterenol and norepinephrine, but not that of dopamine. The effect of dopamine was selectively blocked by spiroperidol (50 μM), a dopamine receptor antagonist, whereas the effects of isoproterenol and norepinephrine were not blocked by spiroperidol. These results suggest that in the rat kidney particulate preparation there is a specific dopamine receptor which can lead to the increase in the concentration of adenosine 3′,5′-monophosphate.