title: Activation of the endoplasmic reticulum Ca2+ pump of pancreatic acini by Ca2+ mobilizing hormones.
abstract: Stimulation of the pancreatic acinar cells with Ca2+ mobilizing hormones increased the ATP-dependent Ca2+ uptake into the ER of permeabilized cells. Activation of the ER Ca2+ pump resulted in increased apparent affinity for Ca2+ from 0.26 to 0.09 uM and Vmax from 2.68 to 5.74 nmoles/mg prot./min. The apparent affinity of the pump for VO4 = was dependent on [Ca2+]. Activation of the pump also decreased apparent affinity for VO4 = from 12 to 32 uM at [Ca2+] of 0.138 uM. These findings suggest that pump activation is due to acceleration of the rate of the conformational transition between the VO4 = (E2) and Ca2+ (E1) sensitive forms of the pump.
mesh_terms: D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002217:Carbachol / Q000494:pharmacology; D002463:Cell Membrane Permeability / Q000187:drug effects; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D007473:Ion Channels / Q000187:drug effects / Q000378:metabolism*; D007700:Kinetics; D010179:Pancreas / Q000648:ultrastructure*; D011487:Protein Conformation; D051381:Rats; D012503:Saponins / Q000494:pharmacology; D012844:Sincalide / Q000494:pharmacology; D014638:Vanadates / Q000378:metabolism / Q000494:pharmacology
chemical_list: D007473:Ion Channels; D012503:Saponins; D014638:Vanadates; D000255:Adenosine Triphosphate; D002217:Carbachol; D012844:Sincalide; D002118:Calcium