Adrenergic stimulation of substrate utilization by cardiac myocytes isolated from rainbow trout.
A method is described for the isolation of calcium-tolerant myocytes from adult rainbow trout. Isolated myocytes remain viable for at least 4 h in suspension as indicated by (1) maintenance of ATP, phosphocreatine (PCr) and glycogen levels; (2) maintenance of the integrity of cell membranes, shown by low rates of leakage of lactate dehydrogenase (LDH) to the medium and exclusion of Trypan Blue; (3) the ability to metabolize substrates; and (4) sensitivity to adrenergic agonists. CO2 production from both glucose and lactate was sensitive to adrenergic stimulation, with the following order of potency: isoproterenol greater than noradrenaline much greater than adrenaline greater than phenylephrine, which indicates the presence of beta 1-adrenoceptors. Myocytes isolated from trout acclimated to 20 degrees C in the summer were more sensitive to beta-adrenergic stimulation than myocytes isolated from trout acclimated to 9 degrees C in either summer or winter. In the absence of exogenous fuel, there was a net reduction in myocyte glycogen content and glycogenolysis was further stimulated by 10(-7) mmol l-1 noradrenaline. However, in the presence of exogenous fuel (either 5 mmol l-1 lactate or 5 mmol l-1 glucose), glycogen was 'spared' and noradrenaline-stimulated glycogenolysis was apparently inhibited.
Department of Zoology, University of Western Ontario, London, Canada.
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Milligan
D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D002118:Calcium / Q000502:physiology; D002245:Carbon Dioxide / Q000378:metabolism; D002395:Catecholamines / Q000494:pharmacology*; D002470:Cell Survival; D005947:Glucose / Q000378:metabolism; D006003:Glycogen / Q000378:metabolism; D066298:In Vitro Techniques; D007773:Lactates / Q000378:metabolism; D009206:Myocardium / Q000166:cytology / Q000378:metabolism*; D010725:Phosphocreatine / Q000378:metabolism; D012621:Seasons; D013565:Sympatholytics / Q000494:pharmacology; D013566:Sympathomimetics / Q000494:pharmacology*; D013696:Temperature; D014337:Trout / Q000502:physiology*
D002395:Catecholamines; D007773:Lactates; D013565:Sympatholytics; D013566:Sympathomimetics; D010725:Phosphocreatine; D002245:Carbon Dioxide; D000255:Adenosine Triphosphate; D006003:Glycogen; D005947:Glucose; D002118:Calcium