title: The mitochondrial high-capacity low-affinity (+/-)-[3H]nitrendipine binding site is regulated by nucleotides.
abstract: The high-capacity, low-affinity (+/-)-[3H]nitrendipine binding site in the inner mitochondrial membrane from guinea-pig heart is regulated by purine and pyrimidine nucleotides. The rank order in (+/-)-[3H]nitrendipine binding inhibition assays (with decreasing potency) was: ATP (IC50 11.8 microM) = adenosine 5'-O-(2-thiotriphosphate (ATP gamma S) greater than 5'-adenylylimidodiphosphate (AppNHp) greater than ADP much greater than GTP = ITP = CTP greater than UTP greater than guanosine 5'-tetraphosphate (GT4P) greater than guanosine 5'-O-(2-thiotriphosphate) (GTP gamma S) greater than 5'-guanylylimidodiphosphate (GppNHp) greater than IDP greater than CDP greater than GDP. There was no effect of AMP, adenosine 3':5'-cyclic monophosphate (cAMP), adenosine, UDP, NAD, and NADP. The ATP effect was fully reversible upon wash-out. Adenine nucleotides and analogs had a (+/-)-[3H]nitrendipine binding inhibition profile in mitochondrial membranes from guinea-pig liver or kidney similar to that obtained in heart mitochondrial membranes. In heart mitochondria, 0.3 mM ATP decreased the Bmax from 1.69 +/- 0.04 nmol/mg protein to 0.73 +/- 0.24 nmol/mg protein whilst it decreased the KD only moderately, from 521 +/- 50 to 352 +/- 43 nM, in equilibrium saturation studies. In kinetic studies, ATP slowed down the dissociation rate of the (+/-)-[3H]nitrendipine binding site complex from 0.016 +/- 0.004 to 0.0042 +/- 0.0002 min-1 but it also decreased the association rate constant from 1.52 +/- 0.15 to 0.41 +/- 0.28 10(4).M-1.min-1, yielding a kinetically determined KD (1024 nM) identical to the control KD (1053 nM).(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Institut für Biochemische Pharmakologie, Innsbruck, Austria.
authors.forename: G
authors.initials: G
authors.lastname: Zernig
authors.forename: T
authors.initials: T
authors.lastname: Moshammer
authors.forename: I
authors.initials: I
authors.lastname: Graziadei
authors.forename: H
authors.initials: H
authors.lastname: Glossmann
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D015220:Calcium Channels; D004095:Dihydropyridines / Q000037:antagonists & inhibitors; D006168:Guinea Pigs; D066298:In Vitro Techniques; D007425:Intracellular Membranes / Q000378:metabolism; D007700:Kinetics; D008928:Mitochondria / Q000378:metabolism*; D009568:Nitrendipine / Q000378:metabolism*; D011685:Purine Nucleotides / Q000378:metabolism*; D011742:Pyrimidine Nucleotides / Q000378:metabolism*; D011978:Receptors, Nicotinic / Q000378:metabolism*
chemical_list: D015220:Calcium Channels; D004095:Dihydropyridines; D011685:Purine Nucleotides; D011742:Pyrimidine Nucleotides; D011978:Receptors, Nicotinic; D000255:Adenosine Triphosphate; D009568:Nitrendipine