Effects of cyclic AMP and of protein kinase on the calcium uptake by various tracheal smooth muscle organelles.

The role of cyclic AMP, if any, in the regulation of smooth muscle tone is not understood. In the present study the effects of cyclic AMP and of protein kinase on the uptake of calcium by "microsomal", "plasma" and "mitochondrial" preparations obtained from bovine tracheal smooth muscle were examined. Cyclic AMP and protein kinase had only a slight and variable effect on the uptake of calcium by microsomes, and no effect on the uptake of calcium by the plasma membrane or the mitochondria. These findings are not compatible with a role of cyclic AMP and protein kinase in the control of the uptake of calcium by the subcellular organelles of tracheal smooth muscle.