Phosphatidylcholine metabolism in hypoxic and phospholipase C exposed rat ventricular myocytes.
A phospholipase C specific for choline and ethanolamine acyl and plasmalogen glycerophospholipids (PC-PLC) has been described in myocardial tissue. In the present study we investigated whether an endogenous PC-PLC is activated in hypoxic, substrate-free incubations of rat ventricular myocytes. The phosphatidylcholine pool of the myocytes was prelabelled with [14C]choline during a 4-h preincubation (pulse) period. The myocytes were subsequently washed and incubated for another 2 h (chase period) in normoxic, hypoxic, or hypoxic buffer supplemented with PC-PLC from Bacillus cereus. We hypothesized that an increase in the total (intracellular plus extracellular) content of [14C]phosphocholine (one of the products resulting from PC-PLC action on phosphatidylcholine) throughout the chase period would indicate PC-PLC activity. Instead, an apparent decrease was observed for this parameter in all myocyte groups (17-29%), even in the one exposed to exogenous PC-PLC. However, 60 min after the start of the chase period, the level of total [14C]phosphocholine was higher in hypoxic (p = 0.022) and hypoxic + PC-PLC exposed (p = 0.013) myocytes compared with normoxic controls. The total content of [14C]choline increased significantly (p < 0.017) in all myocyte groups during the incubation period (98-153%) as a result of an increment of this metabolite in the buffer. Furthermore, the values measured in hypoxic and hypoxic + PC-PLC exposed myocytes during the first hour of the chase period were significantly (p < 0.017) higher than the corresponding values in normoxic myocytes. The present results do not allow firm conclusions regarding endogenous PC-PLC activation in energy-depleted rat cardiac myocytes.(ABSTRACT TRUNCATED AT 250 WORDS)
Myrmel
T
T
Department of Medical Physiology, University of Tromsø, Norway.
Steigen
T K
TK
Bjordal
E
E
Larsen
T S
TS
D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D015687:Cell Hypoxia / Q000502:physiology*; D002478:Cells, Cultured; D002794:Choline / Q000378:metabolism; D002855:Chromatography, Thin Layer; D003600:Cytosol / Q000378:metabolism; D004734:Energy Metabolism / Q000502:physiology; D006352:Heart Ventricles / Q000166:cytology / Q000378:metabolism; D008297:Male; D009206:Myocardium / Q000166:cytology / Q000378:metabolism*; D010713:Phosphatidylcholines / Q000378:metabolism*; D010725:Phosphocreatine / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D010738:Type C Phospholipases / Q000378:metabolism*
D010713:Phosphatidylcholines; D010725:Phosphocreatine; D000255:Adenosine Triphosphate; D010738:Type C Phospholipases; D002794:Choline