Potassium release from the rat submaxillary gland in vitro. III. Effects of pretreatment with reserpine.

The release of K+ from submaxillary gland slices of rats pretreated with reserpine was compared in vitro with that from control slices in paired experiments involving stimulation with catecholamines and with cholinergic secretagogues. The slices were incubated at 37 degrees C in enriched Krebs-Ringer bicarbonate medium gassed with a 95% O2-5% CO2 mixture, in the presence and in the absence of ouabain, Ca++, substrates and specific antagonists. The results indicate that: 1) slices from the treated animals had a similar extent of basal (unstimulated) net K+ release but a significantly higher extent of stimulated net K+ release than control slices; 2) in the presence of ouabain, slices from control and treated animals had similar extents of K+ efflux during basal and stimulated conditions; 3) removal of glucose from the medium resulted in an increased net K+ release from both types of slices, but removal of both glucose and the purines further increased net K+ release from control slices but not from those of treated animals; 4) blockade of receptors 2 minutes after stimulation resulted in a slower rate of K+ reuptake in the slices from treated animals when alpha receptors were blocked with phenolamine but not when cholinergic receptors were blocked with atropine; 5) removal of Ca++ from the medium inhibited the response to norepinephrine and to carbachol, but subsequent addition of Ca++ resulted in a higher extent of net K+ release form the slices of treated animals after norepinephrine, but not carbachol stimulation; 6) there was a 2.57-fold shift to the left and a 3.47-fold shift to the left in the dose-response curve to norepinephrine and carbachol, respectively, after pretreatment with reserpine. It is concluded that reserpine pretreatment: 1) alters the ability of the salivary cells to recover the extruded K+ and 2) induces supersensitivity to secretagogues which is most likely related to changes in the physiological state of the salivary cells.