THE EFFECTS OF KETAMINE ON CA2-MUSCLE CELLS( MOVEMENTS IN A7R5 VASCULAR SMOOTH)

To investigate the effects of ketamine on Ca2+ movement to and from in tracellular Ca2+ stores and across plasma membranes, Ca-45(2+) fluxes were studied in permeabilized and intact A7r5 smooth muscle cells, an established cell line derived from embryonic rat aorta. Monolayers of A7r5 cells were loaded with Ca-45(2+), and the radioactivity in the co llected medium and the residual activity were measured by liquid scint illation counting. Ketamine had no effect on Ca-45(2+) uptake and pass ive leak of the nonmitochondrial Ca2+ pool in permeabilized A7r5 cells . Ketamine 1 mM had no inhibitory effect on the inositol 1,4,5-trispho sphate (InsP(3), 1 mu M)-induced Ca2+ release from the intracellular s tores. In intact A7r5 cells, ketamine did not alter the Ca2+ extrusion from these cells under resting conditions. Addition of 10 nM vasopres sin resulted in a transient Ca2+ release from the intracellular stores . Ketamine inhibited this vasopressin-induced Ca2+ release, but did no t enhance Ca2+ extrusion through the plasma membrane in the period aft er the vasopressin effect. These results indicate that ketamine inhibi ts agonist-induced Ca2+ release from intracellular stores, but has no effect on Ca2+-uptake into intracellular stores or on Ca2+ extrusion t hrough the plasma membrane in A7r5 smooth muscle cells.