Active transport of organic acids in the proximal tubules of the surviving rat kidney normally and under various influences. II. The effect of exogenous cyclic 3',5'-AMP and of substances that alter its intracellular concentration]

Exogenous cyclic 3',5'-AMP (cAMP) and substances known to increase the intracellular concentration of this nucleotide (isoproterenol, theophylline, noradrenaline, lactate) were shown to inhibit the transport of fluorescein (a weak organic acid) into the rat renal proximal tubules at 20 degrees C. Carbacholine decreasing intracellular cAMP concentration stimulated the transport. Propranolol, a beta-adrenergic blockator, diminished significantly the inhibitory effect of noradrenaline on the transport. Lactate and carbacholine when added simultaneously, neutralize their action. The inhibitory action of intracellular cAMP on the transport is supposed to be a result of the diminition of a pool of endogenous weak organic acids which may take part in the exchange of diffusion with the marker anion across basal plasma membrane.