Modulation of uncoupler-induced sugar uptake in isolated adult rat heart cells by isoproterenol.
When cells (2.4 mg/ml) in the presence of glucose were exposed to 0.15 microM p-trifluoromethoxyphenylhydrazone (FCCP), the time until 50% of the rod-shaped cells had undergone contracture was more than twice as long for cells without isoproterenol as for cells with isoproterenol. The cause of this large effect was revealed in experiments without glucose where 3-O-methylglucose entry, ATP levels, and cellular configuration were measured simultaneously. It was found that the onset of contracture was almost coincident with the decline in total measured ATP, suggesting that, in any cell, contracture was accompanied by a sudden and total ATP loss. In control cells, FCCP stimulated 3-O-methylglucose entry at or before the time this ATP catastrophe occurred. In cells exposed to isoproterenol, however, the stimulation of 3-O-methylglucose entry by FCCP did not occur until after the ATP catastrophe, and the extent of stimulation was reduced. This suggests that, when glucose was present, the FCCP-induced glucose influx was sufficient to significantly delay the onset of contracture in control cells but not in cells treated with isoproterenol. This conclusion was borne out by the observation that the effect of isoproterenol on contracture could be overcome with insulin.
D019325:3-O-Methylglucose; D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D002259:Carbonyl Cyanide p-Trifluoromethoxyphenylhydrazone / Q000494:pharmacology; D004789:Enzyme Activation / Q000187:drug effects; D005947:Glucose / Q000378:metabolism*; D066298:In Vitro Techniques; D007328:Insulin / Q000494:pharmacology; D007545:Isoproterenol / Q000494:pharmacology*; D008757:Methylglucosides / Q000378:metabolism; D009206:Myocardium / Q000378:metabolism*; D010762:Phosphorylase a / Q000378:metabolism; D051381:Rats
D007328:Insulin; D008757:Methylglucosides; D019325:3-O-Methylglucose; D002259:Carbonyl Cyanide p-Trifluoromethoxyphenylhydrazone; D000255:Adenosine Triphosphate; D010762:Phosphorylase a; D005947:Glucose; D007545:Isoproterenol