title: Differential blockade of agonist- and depolarization-induced 45Ca2+ influx in smooth muscle cells.
abstract: ATP stimulated 45Ca2+ influx in rat aortic smooth muscle cells in a concentration-dependent manner (EC50 = 3.6 +/- 0.5 X 10(-7) M). ADP and GTP were less effective than ATP in stimulating 45Ca2+ influx; AMP was weakly active and the adenosine agonist 5'-(N-ethyl-carboxamido)-adenosine (NECA) had no effect. ATP gamma S was about equieffective with ATP, whereas alpha,beta-methylene-ATP (APCPP) did not induce 45Ca2+ influx. Stimulation of 45Ca2+ influx by ATP was not abolished by the dihydropyridine Ca2+ channel antagonist darodipine (PY 108-068), which completely blocked depolarization-induced 45Ca2+ influx. Inorganic cations (La3+, Cd2+, Co2+, Ni2+, Mn2+, and Mg2+) were able to inhibit both agonist- and depolarization-induced 45Ca2+ influx. Cd2+, however, was approximately 20 times more selective in blocking K+-stimulated than agonist-stimulated 45Ca2+ influx. These data indicate that ATP-stimulated Ca2+ influx in rat aortic smooth muscle cells is resistant to darodipine but is reduced by La3+, Cd2+, and other inorganic blockers of Ca2+ channels.
authors.affiliation: Preclinical Research, Sandoz Limited, Basel, Switzerland.
authors.forename: A
authors.initials: A
authors.lastname: Wallnöfer
authors.forename: C
authors.initials: C
authors.lastname: Cauvin
authors.forename: T W
authors.initials: TW
authors.lastname: Lategan
authors.forename: U T
authors.initials: UT
authors.lastname: Rüegg
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism / Q000494:pharmacology; D000818:Animals; D001011:Aorta / Q000502:physiology; D001127:Arginine Vasopressin / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D002132:Calcium Radioisotopes; D002412:Cations; D002478:Cells, Cultured; D007700:Kinetics; D008564:Membrane Potentials; D009131:Muscle, Smooth, Vascular / Q000502:physiology*; D011188:Potassium / Q000494:pharmacology; D011865:Radioisotope Dilution Technique; D051381:Rats; D012265:Ribonucleotides / Q000494:pharmacology*
chemical_list: D002132:Calcium Radioisotopes; D002412:Cations; D012265:Ribonucleotides; D001127:Arginine Vasopressin; D000255:Adenosine Triphosphate; D011188:Potassium; D002118:Calcium