Regulation by thapsigargin and carbachol of the intracellular calcium concentration in rat submandibular glands.

1. Carbachol and thapsigargin both increased the intracellular calcium concentration in rat submandibular cells in the presence and in the absence of extracellular calcium. Depletion of intracellular calcium pools with thapsigargin prevented the response to carbachol. 2. The two agents also increased the influx of calcium. The muscarinic agonist stimulated the efflux of calcium outside the cell. 3. From these results it is concluded that submandibular cells possess several intracellular calcium pools sensitive to thapsigargin, among which some are sensitive to IP3. Depletion of these pools increase the uptake of extracellular calcium.