Calcium homeostasis and nerve growth factor secretion from vascular and bladder smooth muscle cells

Bladder and vascular smooth muscle cells cultured from four rat strains (WK Y, SHR, WKHA, WKHT) differing in rates of nerve growth factor (NGF) product ion were used to determine whether a relationship exists between intracellu lar calcium and NGF secretion. Basal cytosolic calcium was related to basal NGF secretion rates in bladder and vascular smooth muscle cells from all f our strains with the exception of WKHT bladder muscle cells. Thrombin is a calcium-mobilizing agent and increases NGF production from vascular but not bladder smooth muscle cells. Strain differences were found in the magnitud e of the calcium peak induced by thrombin in vascular smooth muscle cells, but these differences did not correlate with NGF secretion. Thrombin caused a calcium response in bladder smooth muscle cells without influencing NGF production. Quenching the calcium transient with a calcium chelator had no effect on thrombin-inducted NGF secretion rates in vascular smooth muscle c ells. Thus, basal intracellular calcium may establish a set point for NGF s ecretion from smooth muscle. In addition, transient elevations in cytosolic calcium were unrelated to the induction of NGF output.