title: Effect of adenosine and its analogues on calcium influx in coronary artery.
abstract: In the present study, we have investigated the changes in calcium influx during the relaxing responses to adenosine and its analogues. Calcium-45 influx was measured in bovine coronary artery rings in the presence of prostaglandin F2 alpha (10(-5) M) and KCl (50 and 100 mM). Prostaglandin F2 alpha and KCl caused increases in calcium influx. Prostaglandin F2 alpha produced a further contraction when added to rings maximally contracted with KCl (100 mM or higher), suggesting two different mechanisms for prostaglandin F2 alpha- and KCl-induced contractions. Similarly, a greater calcium influx was observed when prostaglandin F2 alpha was mixed with KCl (50 or 100 mM). At all the concentrations tested, adenosine and its analogues [5'-(N-ethyl-carboxamidoadenosine, NECA; N6-(L-2-phenylisopropyl)adenosine, L-PIA] significantly inhibited prostaglandin F2 alpha-induced increases in calcium influx. However, only higher concentrations of adenosine, NECA, and L-PIA inhibited 100 mM KCl-induced calcium influx. Previous treatment with 8-phenyltheophylline blocked the inhibitory actions of adenosine, NECA, and L-PIA on calcium influx. The inhibition of calcium influx by adenosine, NECA, and L-PIA correlated well with their relaxing ability in the presence of prostaglandin F2 alpha. The data suggest that prostaglandin F2 alpha-induced calcium influx was more sensitive to the action of adenosine and its analogues than the calcium influx induced by high K+ depolarization.
authors.affiliation: Department of Pharmacology, School of Medicine, East Carolina University, Greenville, North Carolina 27858-4354.
authors.forename: M V
authors.initials: MV
authors.lastname: Ramagopal
authors.forename: S J
authors.initials: SJ
authors.lastname: Mustafa
mesh_terms: D000241:Adenosine / Q000031:analogs & derivatives* / Q000494:pharmacology*; D019830:Adenosine-5'-(N-ethylcarboxamide); D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002417:Cattle; D003331:Coronary Vessels / Q000187:drug effects / Q000378:metabolism*; D015237:Dinoprost / Q000494:pharmacology; D066298:In Vitro Techniques; D007700:Kinetics; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000378:metabolism*; D010660:Phenylisopropyladenosine / Q000494:pharmacology*; D011189:Potassium Chloride / Q000494:pharmacology
chemical_list: D010660:Phenylisopropyladenosine; D019830:Adenosine-5'-(N-ethylcarboxamide); D011189:Potassium Chloride; D015237:Dinoprost; D000241:Adenosine; D002118:Calcium