Calcium incorporation by canine aortic smooth muscle microsomes.
The accumulation of calcium (Ca2+) and factors influencing Ca2+ incorporation in vascular smooth muscle were examined in a microsomal fraction prepared from canine aortae. The accumulation of Ca2+ required the presence of ATP and increased over time. Furthermore, the incorporation of 45Ca into the microsomal preparation was stimulated both in the presence of oxalate and when the Ca2+ concentration of the bathing media was elevated from 20 micron to 40 micron. Calcium uptake (with oxalate) was temperature-dependent; uptake was unaffected by azide. Both lanthanum (La3+) and phosphatidyl serine (PS) inhibited ATP-dependent uptake in a concentration-dependent manner. In the presence of ATP, calcium binding (without oxalate) was slightly inhibited by La3+, whereas PS had no effect under these conditions. When ATP was removed from the incubation medium, the presence of PS stimulated both the uptake and binding of 45Ca, whereas La3+ decreased both uptake and binding. These findings support the idea that La3+ binds on the surface of the vesicles and, in this manner, decreases available Ca2+ sites, whereas PS appears to increase the number of Ca2+ sites by either entering the membranes or adsorbing on it.
D000255:Adenosine Triphosphate / Q000502:physiology; D000818:Animals; D001013:Aorta, Thoracic / Q000378:metabolism / Q000648:ultrastructure; D001386:Azides / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D003080:Cold Temperature; D004285:Dogs; D005260:Female; D005615:Freezing; D066298:In Vitro Techniques; D007811:Lanthanum / Q000494:pharmacology; D008297:Male; D008861:Microsomes / Q000378:metabolism*; D009130:Muscle, Smooth / Q000378:metabolism* / Q000648:ultrastructure; D010070:Oxalates / Q000494:pharmacology; D010718:Phosphatidylserines / Q000494:pharmacology; D011506:Proteins / Q000378:metabolism
D001386:Azides; D010070:Oxalates; D010718:Phosphatidylserines; D011506:Proteins; D007811:Lanthanum; D000255:Adenosine Triphosphate; D002118:Calcium