Secretory response of dispersed rat submandibular cells. I. Potassium release

The secretory response of dispersed rat submandibular cells as it relates to the net efflux of K+ following sympathomimetic and parasympathomimetic stimulation was evaluated. The cholinergic agonists acetylcholine and carbamylcholine were found to have equal efficacy but dissimilar receptor affinity. Median effective concentrations (EC50's) were 1.7 x 10(-7) M and 7.1 x 10(-7) M, respectively. Pilocarpine was found to be acting as a "partial" agonist and had an EC50 at 5.6 x 10(-7) M. (-)-Norepinephrine and (-)-epinephrine were found to have similar efficacy and potency with EC50's at 5.6 x 10(-7) M and 3.8 x 10(-7) M, respectively. (-)-Phenylephrine was found to act as a partial agonist with an EC50 at 3.8 x 10(-6) M, whereas (-)-isoproterenol stimulation resulted in no net K+ efflux within the concentrations tested (10(-8) M--10(-3) M). Extracellular Ca2+, but not Mg2+, was shown to be required to elicit a net K efflux following either cholinergic or alpha-adrenergic stimulation.