Amylase release from rat parotid glands II. Calcium kinetics

The kinetics of ⁴⁵Ca²⁺ uptake, efflux, and calcium potentiation of amylase release by slices of rat parotid glands were examined. Pretreatment of the tissue with 11.25 mM ⁴⁵Ca²⁺ medium increased the total tissue ⁴⁵calcium content. Lanthanum (1 mM) decreased tissue uptake, blocked the slow components of exchange and appeared to inhibit transcellular calcium movement. Neither dibutyryl cyclic AMP nor caffeine caused consistently significant effects on ⁴⁵Ca²⁺ kinetics, or total ⁴⁵calcium content. Carbamylcholine increased the initial rate of ⁴⁵Ca²⁺ uptake, but had no effect on total uptake.Elevation of the extracellular Ca²⁺ concentration to 11.25 mM during stimulation of amylase release resulted in an initial decrease in the rate of amylase release followed by a potentiation of release which developed slowly, requiring 40–50 min to reach the maximal response.The inability to detect release-related changes in either calcium influx or mobilization, and the lengthy times and high Ca²⁺ concentrations required to achieve calcium potentiation suggests that calcium does not couple amylase release.