Potassium release from the rat submaxillary gland in vitro. II. Induction by parasympathomimetic secretagogues.
The kinetics of K+ release from an in vitro system of rat submaxillary gland slices were studied after stimulation with parasympathomimetic secretagogues. The slices were incubated at 37degreesC in an oxygenated, enriched Krebs-Ringer bicarbonate medium in the presence and in the absence of Ca++ and of ouabain and, in some experiments, in the presence of the specific antagonists atropine (5 x 10(-6) and 2 x 10(-5) M), phentolamine (2 x 10(-5) M) or propranolol (2 x 10(-5) M. K+ release was elicited by the addition of acetylcholine (2 x 10(-5) M), pilocarpine (2 x 10(-5) M) and carbamylcholine (10(-9) to 2 x 10(-5) M). The results demonstrate that: 1) The selective stimulation of cholinergic receptors induces a rapid net release of K+ from the slices. After 10 minutes of incubation, the percent K+ released after a 2 x 10(-5) M dose of each of the three secretagogues was, respectively, 20.8%, 15.5%, and 19%. 2) The response to carbamylcholine does not occur when Ca++ is absent from the medium and is blocked by atropine but not by phentolamine or by propranolol. Atropine (5 x 10(-6) M) causes a 17-fold shift to the right on the dose-response curve to carbamylcholine. 3) The magnitude of K+ release is the ratio of two opposing mechanisms, a passive efflux and an active reuptake. The latter depends on the activity of the ouabain-sensitive Na+-K+-adenosine triphosphatase. 4) The sensitivity of the slice system to carbamylcholine seems to be greater than that to norepinephrine in terms of net K+ release after equimolar doses of 2 x 10(-5) M and also in terms of the dose required to induce a half maximal passive K+ efflux. However, the maximal passive K+ efflux is similar after both types of secretagogue and amounts of approximately 45% of the K+ present in the slices.
D000109:Acetylcholine / Q000494:pharmacology; D000251:Adenosine Triphosphatases / Q000037:antagonists & inhibitors; D000818:Animals; D001285:Atropine / Q000494:pharmacology; D002118:Calcium / Q000494:pharmacology; D002217:Carbachol / Q000494:pharmacology; D066298:In Vitro Techniques; D007700:Kinetics; D008297:Male; D010042:Ouabain / Q000494:pharmacology; D010277:Parasympathomimetics / Q000494:pharmacology*; D010862:Pilocarpine / Q000494:pharmacology; D011188:Potassium / Q000378:metabolism*; D051381:Rats; D013268:Stimulation, Chemical; D013363:Submandibular Gland / Q000187:drug effects / Q000378:metabolism*; D013997:Time Factors
D010277:Parasympathomimetics; D010862:Pilocarpine; D010042:Ouabain; D001285:Atropine; D002217:Carbachol; D000251:Adenosine Triphosphatases; D000109:Acetylcholine; D011188:Potassium; D002118:Calcium