title: Effects of vasodilator drugs, alkaline phosphatase, and cyclic AMP-dependent protein kinase on the 45calcium uptake of sarcolemmal microsomes from human umbilical arteries.
abstract: 1 A microsomal fraction was prepared from human umbilical arteries by differential centrifugation. The preparation was capable of an oxalate-stimulated Ca2+ uptake at a mean rate of 0.74 nmol Ca2+ mg-1 protein min-1 which could be inhibited by a Ca2+ ionophore, A 23 187, and by Tween 80. 2 The rate of Ca2+ uptake in the fraction obtained by density gradient fractionation paralleled 5'-nucleotidase activity suggesting that vesicles of predominantly sarcolemmal origin were responsible for the microsomal Ca2+ uptake. 3 Cyclic adenosine 3',5'-monophosphate-dependent protein kinase enhanced membrane phosphorylation but did not affect Ca2+ uptake. Preincubation with alkaline phosphatase reduced membrane phosphorylation to a greater extent than Ca2+ uptake. These data are not in favour of a close correlation between Ca2+ uptake and phosphorylation. 4 None of 15 vasodilator drugs (bencyclane, carbocromen, diazoxide, dilazep, hydralazine, indapamide, isosorbide dinitrate, methyl-isobutyl-xanthine, minoxidil, naftidrofuryl, nitroglycerine, prenylamine, sodium nitroprusside, tetracaine, and verapamil) had any effect on Ca2+ uptake at 10(-5) M. This suggests that vasodilator drugs do not act by a direct influence on the Ca2+ pumps of vascular smooth muscle cells.
mesh_terms: D000469:Alkaline Phosphatase / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism*; D000242:Cyclic AMP / Q000494:pharmacology; D006801:Humans; D066298:In Vitro Techniques; D008861:Microsomes / Q000378:metabolism*; D009131:Muscle, Smooth, Vascular / Q000378:metabolism*; D010766:Phosphorylation; D011494:Protein Kinases / Q000494:pharmacology*; D012508:Sarcolemma / Q000378:metabolism; D014469:Umbilical Arteries / Q000378:metabolism; D014665:Vasodilator Agents / Q000494:pharmacology*
chemical_list: D014665:Vasodilator Agents; D000242:Cyclic AMP; D011494:Protein Kinases; D000469:Alkaline Phosphatase; D002118:Calcium