ANP-STIMULATED CGMP EGRESSION IN RENAL PRINCIPAL CELLS - ABROGATION OF POLARITY BY SV40 LARGE-T

Egression of atrial natriuretic peptide (ANP)-stimulated guanosine 3', 5'-cyclic monophosphate (cGMP) was compared with that of isoproterenol -stimulated adenosine 3',5'-cyclic monophosphate (cAMP) in a rabbit co llecting duct cell line transformed with a temperature-sensitive strai n of simian virus 40 (SV40). At 39.5 degrees C (inactivated large T), cells exhibit major features of principal cells, whereas at 33 degrees C (functional large T) they lose most of their specific properties. W hen cells were grown on plastic at 39.5 degrees C, both cyclic nucleot ides were predominantly released extracellularly via probenecid-sensit ive carriers. Probenecid (3 mM) reduced the ratios of extracellular cG MP and cAMP by 84 and 70%, respectively. The amount of extracellular c GMP or cAMP was linearly correlated with the time integral of the intr acellular cyclic nucleotide, suggesting first-order kinetics. The appa rent first-order rate constant (k) was sixfold greater for cGMP (0.139 +/- 0.037 min(-1), n = 3 experiments) than for cAMP (0.022 +/- 0.003( -1), n = 3 experiments). 3-Isobutyl-1-methylxanthine markedly inhibite d extrusion of cGMP (k = 0.022 +/- 0.003 min(-1)), whereas that of cAM P was unchanged. When cells were grown on filters at 39.5 degrees C, b oth nucleotides were predominantly released in the apical medium but w ith a greater polarity for cGMP (83 +/- 4%, n = 6 experiments) than fo r cAMP (60 +/- 6%, n = 3 experiments) and a prevailing apical localiza tion of the probenecid-sensitive carrier. Activation of SV40 large T a t 33 degrees C did not alter cyclic nucleotide transport characteristi cs but abolished the polarity of probenecid-sensitive cyclic nucleotid e extrusion. These results suggest a physiological role for luminal cG MP in the rabbit collecting duct and a specific effect of large T on t he probenecid-sensitive carrier polarity.