Effects of hypoxia on lipolysis in isolated rat myocardial cells.
The effect of hypoxia on myocardial lipolysis (glycerol release) was investigated in freshly isolated, calcium-tolerant rat ventricular myocytes. Hypoxia was produced by gassing the incubation medium (Joklik-minimum essential medium, supplemented with 1.2 mM MgSO4, 1 mM DL-carnitine, 1.5 mM CaCl2 and 0.6 mM palmitate bound to 0.15 mM fatty acid free bovine serum albumin) with 95% N2-5% CO2. Control (normoxic) incubations were carried out under air-5% CO2 atmosphere. Basal glycerol release increased from 46.6 +/- 3.0 nmol/10(6) cells.30 min in normoxia to 64.5 +/- 4.3 nmol/10(6) cells.30 min in hypoxia (p less than 0.05). Addition of isoprenaline (10 microM) resulted in a significant (p less than 0.05) stimulation of the glycerol release both in normoxia and in hypoxia, but the enhancement above basal rates was apparently lower in hypoxia (8.7 +/- 2.5 nmol/10(6) cells.30 min) than in normoxia (12.2 +/- 2.7 nmol/10(6) cells.30 min). Furthermore, whereas the isoprenaline-induced rise in lipolysis both in normoxia and hypoxia was prevented by inclusion of propranolol (10 microM), propranolol did not affect the hypoxia-induced increase in lipolysis. Thus, the above findings suggest that myocardial lipolysis may be stimulated by local non-adrenergic mechanisms during hypoxia.
Larsen
T S
TS
Department of Physiology, University of Tromsø, Norway.
Myrmel
T
T
Skulberg
A
A
Severson
D L
DL
Mjøs
O D
OD
D000818:Animals; D002478:Cells, Cultured; D005990:Glycerol / Q000378:metabolism; D007545:Isoproterenol / Q000494:pharmacology; D008066:Lipolysis / Q000187:drug effects; D009206:Myocardium / Q000378:metabolism*; D010100:Oxygen / Q000502:physiology*; D051381:Rats; D011919:Rats, Inbred Strains
D007545:Isoproterenol; D005990:Glycerol; D010100:Oxygen