title: [Influence of Ca2+ on kinetic parameters of pancreatic acinar mitochondria in situ respiration].
abstract: The dependence of respiration rate of rat permeabilized acinar pancreacytes on oxidative substrates concentration was studied at various [Ca2+] - 10-8-10-6 M. Pancreacytes were permeabilized with 50 microg of digitonin per 1 million cells. Respiration rate was measured polarographically using the Clark electrode at oxidation of succinate or pyruvate either glutamate in the presence of malate. Parameters of Michaelis-Menten equation were calculated by the method of Cornish-Bowden or using Idi-Hofsti coordinates and parameters of Hill equation - using coordinates {v; v/[S]h}. In the studied range of [Ca2+] the kinetic dependence of respiration at pyruvate oxidation is described by the Michaelis-Menten equation, and at oxidation of succinate or glutamate - by Hill equation with h = 1.11-1.43 and 0.50-0.85, respectively. The apparent constant of respiration half-activation (K0.5) did not significantly change in the studied range of [Ca2+] while at 10-7 M Ca2+ it was 0.90 +/- 0.06 mM for succinate, 0.096 +/- 0.007 mM for pyruvate and 0.34 +/- 0.03 mM for glutamate. Maximum respiration rate Vax at pyruvate oxidation increased from 0.077 +/- 0.002 to 0.119 +/- 0.002 and 0.140 +/- 0.002 nmol O2/(s.million cells) due to the increase of [Ca2+] from 10-7 to 5x10-7 or 10-6 M, respectively. At oxidation of succinate or glutamate Ca2+ did not significantly affect Vmax Thus, the increase of [Ca2+] stimulates respiration of mitochondria in situ of acinar pancreacytes at oxidation of exogenous pyruvate (obviously due to pyruvate dehydrogenase activation), but not at succinate or glutamate oxidation.
authors: B O
authors: BO
authors: Man'ko
authors: V V
authors: VV
authors: Man'ko
mesh_terms: D061354:Acinar Cells / Q000737:chemistry / Q000187:drug effects / Q000378:metabolism*; D000818:Animals; D002118:Calcium / Q000378:metabolism* / Q000494:pharmacology; D002458:Cell Fractionation; D018698:Glutamic Acid / Q000378:metabolism; D007700:Kinetics; D008293:Malates / Q000378:metabolism; D008297:Male; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism*; D010085:Oxidative Phosphorylation / Q000187:drug effects*; D010179:Pancreas / Q000737:chemistry / Q000187:drug effects / Q000378:metabolism*; D011048:Polarography; D019289:Pyruvic Acid / Q000378:metabolism; D051381:Rats; D019802:Succinic Acid / Q000378:metabolism
chemical_list: D008293:Malates; D018698:Glutamic Acid; C030298:malic acid; D019289:Pyruvic Acid; D019802:Succinic Acid; D002118:Calcium