title: Evidence against a role for guanosine 3',5'-cyclic monophosphate in rat submandibular salivary gland potassium release.
abstract: The role of guanosine 3',5'-cyclic monophosphate (cGMP) in the net K+ efflux following parasympathomimetic and sympathomimetic stimulation in dispersed rat submandibular cells was evaluated. In unstimulated cells, approx. 70 per cent of the total cGMP content was present in the incubation medium; the addition of 1-methyl-3-isobutylxanthine (MIX), a phosphodiesterase inhibitor, to the medium elevated both intracellular and extracellular levels of cGMP. Cholinergic receptor stimulation resulted in a rapid increase of the cGMP content in the cells and in the medium. Extracellular Ca2+ was necessary for an increased cGMP response and MIX potentiated the cGMP response. Adrenergic-receptor activation produced a slight increase in cGMP after 5 min of stimulation but only when MIX was present in the medium. cGMP analogues (8-Br-cGMP and Bt2cGMP) had no effect on the rate of maximal net K+ efflux, on submaximal net K+ efflux, or on K+ re-uptake following parasympathomimetic or sympathomimetic stimulation. The dose-response relationship for a cholinergic agonist, carbamylcholine, or an adrenergic agonist, norepinephrine, was unaffected by the presence of either 8-Br-cGMP or Bt2cGMP in the medium. MIX, at a concentration sufficient to increase intracellular and extracellular cGMP levels, had no effect on net K+ efflux. These data do not support a role for cGMP in modulating rat submandibular potassium release.
mesh_terms: D015056:1-Methyl-3-isobutylxanthine / Q000494:pharmacology; D000818:Animals; D006152:Cyclic GMP / Q000031:analogs & derivatives / Q000378:metabolism* / Q000494:pharmacology; D009638:Norepinephrine / Q000494:pharmacology; D010277:Parasympathomimetics / Q000494:pharmacology; D011188:Potassium / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D013363:Submandibular Gland / Q000378:metabolism*; D013566:Sympathomimetics / Q000494:pharmacology
chemical_list: D010277:Parasympathomimetics; D013566:Sympathomimetics; C016276:8-bromocyclic GMP; D006152:Cyclic GMP; D011188:Potassium; D015056:1-Methyl-3-isobutylxanthine; D009638:Norepinephrine