Cholinergic modulation of water transport in the toad bladder.
The effect of carbachol on water transport by the toad bladder was studied. Carbachol caused a small increase in base-line water flow and inhibited, partially, vasopressin- (AVP) or cyclic AMP-stimulated water flow. The effect of carbachol on base-line or AVP-stimulated water flow was totally prevented by atropine, indicating that the effect of cabachol on water transport is mediated through a muscarinic receptor. Carbachol caused a significant increase in 45Ca uptake by toad bladder; this increase in calcium uptake could be prevented by atropine, pentobarbital, or lanthanum. The effect of carbachol on base-line and AVP-stimulated water flow was also prevented by pentobarbital or lanthanum, suggesting that the effect of carbachol is mediated, at least in part, by an increase in calcium uptake. The ionophore A-23187, an agent that increased 45Ca uptake, also enhanced base-line water flow and inhibited AVP-stimulated water flow. The effects of carbachol and the ionophore A-23187 on base-line water flow, AVP-stimulated water flow, and on calcium uptake were not additive, suggesting that both agents alter water transport by a similar mechanism. These data demonstrate that carbachol stimulates base-line water transport and inhibits AVP-stimulated water transport. They suggest that the alteration in water transport induced by carbachol is related to an increase in calcium uptake.
D000818:Animals; D001285:Atropine / Q000494:pharmacology; D001692:Biological Transport / Q000187:drug effects; D002024:Bufo marinus / Q000378:metabolism; D000001:Calcimycin / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism; D002132:Calcium Radioisotopes; D002217:Carbachol / Q000494:pharmacology*; D066298:In Vitro Techniques; D007811:Lanthanum / Q000494:pharmacology; D010424:Pentobarbital / Q000494:pharmacology; D001743:Urinary Bladder / Q000378:metabolism*; D014867:Water / Q000378:metabolism*
D002132:Calcium Radioisotopes; D014867:Water; D000001:Calcimycin; D007811:Lanthanum; D001285:Atropine; D002217:Carbachol; D010424:Pentobarbital; D002118:Calcium