title: Effects of ATP on specific [3H](+)-isradipine binding in rat ventricular cardiomyocytes.
abstract: In heart membranes, specific [3H](+)-isradipine binding is reduced in membranes from ischemic hearts and by adding 1 mM ATP at low Ca2+ concentrations (1 microM). We investigated if ATP affected specific [3H](+)-isradipine binding in intact rat ventricular cardiomyocytes. Reducing intracellular ATP by 2 h hypoxia (N2 gas) and glucose-free buffer with 1 mM CN-, did not affect density or dissociation constant of [3H](+)-isradipine binding in cardiomyocytes at extracellular 30 mM K+. Extracellular 10 mM ATP inhibited binding in cardiomyocytes by 90% and 50%, respectively, in 30 mM and 120 mM K+ buffer with Ca2+ and Mg2+. Omitting Ca2+ and Mg2+ from the buffer had no effect on the binding inhibition of ATP. Hence, in cardiomyocytes, reducing intracellular ATP has no effect on specific [3H](+)-isradipine binding, whereas high extracellular ATP in the presence of Ca2+ and Mg2+ inhibits binding. Apparently, ATP effects on binding differ in cardiomyocytes and membranes.
authors.affiliation: Clinical Chemistry Department, Ullevål University Hospital, Oslo, Norway.
authors.forename: M
authors.initials: M
authors.lastname: Stokke
authors.forename: E M
authors.initials: EM
authors.lastname: Hagelin
authors.forename: O
authors.initials: O
authors.lastname: Brørs
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism / Q000494:pharmacology*; D000818:Animals; D015220:Calcium Channels / Q000187:drug effects* / Q000378:metabolism*; D015687:Cell Hypoxia / Q000502:physiology; D006321:Heart / Q000187:drug effects*; D006352:Heart Ventricles / Q000187:drug effects / Q000378:metabolism; D017275:Isradipine / Q000378:metabolism*; D008274:Magnesium / Q000378:metabolism; D008297:Male; D009206:Myocardium / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar
chemical_list: D015220:Calcium Channels; D000255:Adenosine Triphosphate; D008274:Magnesium; D017275:Isradipine