Sodium nitroprusside induced cGMP accumulation in isolated frog skin epithelium. Effect on cAMP, hydroosmotic and natriferic response to antidiuretic horomone.

Abstract

The cGMP content of isolated frog skin epithelia has been measured, and the basal level was found to be 14.3 +/- 1.7 fmol/mg dry lweight. 0.1 mM sodium nitroprusside induced a 10-fold increase in the cGNP level within 5 min after which it rose more slowly. The maximum increase in cGMP level was obtained with 1 mM sodium nitroprusside, giving a 20-50-fold increase. 1 mM sodium nitroprusside per se had no effect on osmotic water flow or active sodium transport. On the other hand, the osmotic water flow response to arginine vasotocin was somewhat enhanced in skins which had been pretreated with 1 mM sodium nitroprusside; thus the water flow responses to 1 and 31 ng/ml arginine vasotocin were on the average 31 and 14% higher in skins exposed to sodium nitroprusside than in control skins. Sodium nitroprusside had no effect on the increment in sodium transport rate elicited by arginine vasotocin. Sodium nitroprusside alone increased the cAMP level slightly; the enhanced cAMP level, reached after 30 min incubation with 40 ng/ml arginine vasotocin, was 20% higher in the presence of 1 mM sodium nitroprusside. cGMP has no effect on osmotic water flow nor on active sodium transport and is not involved in the regulation of sodium transport by antidiuretic hormone. However, cGMP (or sodium nitroprusside) has a moderate effect on the hormone-stimulated osmotic water flow.