Effects of Ca2+ and calmodulin antagonists on the oxygen uptake induced by acetylcholine or substance P in rat submandibular gland slices.

Effects of Ca2+ and calmodulin antagonists on the oxygen uptake induced by acetylcholine (ACh) or substance P (SP) were investigated in rat submandibular gland slices. The oxygen uptake induced by ACh or SP was significantly inhibited by removing Ca2+ from the medium and the slices. The oxygen uptake by ACh in the Ca2+-deficient slices was almost completely recovered by the addition of 3.0 and 5.0 mM Ca2+, whereas that by SP was not recovered by the addition of 3.0 mM Ca2+, but recovered by 5.0 mM Ca2+. Ca2+ antagonists, diltiazem, verapamil and La3+, significantly inhibited the ACh-induced oxygen uptake. On the other hand, the SP-induced oxygen uptake was inhibited by diltiazem and La3+, but not by verapamil. Calmodulin antagonists, trifluoperazine, chlorpromazine and W-7, had no inhibitory effects on the ACh-induced oxygen uptake. The SP-induced oxygen uptake was not affected by trifluoperazine, chlorpromazine and low concentrations of W-7, but was inhibited by high concentrations of W-7. These results suggest that the ACh- or SP-induced oxygen uptake is dependent on the presence and permeability of Ca2+ with a subtle difference between the ACh and the SP mechanisms and that the oxygen uptake is independent of calmodulin.