51. EFFECTS OF PHOSPHOLIPASE C ON ACTION POTENTIALS AND INTRACELLULAR Ca2+ CONCENTRATION IN GUINEA PIG HEART
- Author
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Hajime Terada, Haruo Miyata, Hiroshi Satoh, Akira Kobayashi, Naohisa Noda, Noboru Yamazaki, and Hideharu Hayashi
- Subjects
Male ,medicine.medical_specialty ,Fura-2 ,Physiology ,Guinea Pigs ,Myocardial Ischemia ,Ischemia ,Action Potentials ,Myocardial Reperfusion Injury ,In Vitro Techniques ,Biology ,Phospholipase ,Guinea pig ,chemistry.chemical_compound ,Phospholipase C ,Internal medicine ,medicine ,Animals ,Cell Size ,Myocardium ,Ca2+ overload ,Heart ,medicine.disease ,Intracellular Ca2+ concentration ,Electrophysiology ,Endocrinology ,chemistry ,Type C Phospholipases ,Calcium ,Delayed afterdepolarization ,Cardiology and Cardiovascular Medicine ,Perfusion ,Intracellular - Abstract
To clarify the role of phospholipase C (PLC) in arrythmias and cell injury during myocardial ischemia/reperfusion, we studied its effects on electrophysiology and [Ca2+]i in guinea pig hearts. After exposure to PLC (1 and 2 U/ml), the action potential durations of right ventricular papillary muscles were decreased. Delayed afterdepolarizations were observed in all of the preparations, and some developed into triggered activities. Developed tension decreased after an initial increase for the first 5 min, while resting tension increased consistently. The effects of PLC (0.02, 0.1, and 0.2 U/ml) on [Ca2+]i of ventricular myocytes were measured using fura-2 fluorescence. The ratio of rod-shaped cells to all cells decreased in a time- and a concentration-dependent manner. Perfusion with 0.1 U/ml PLC elevated [Ca2+]i from 56 +/- 5 nM to 245 +/- 47 nM before cell rounding, and to 1167 +/- 172 nM after cell rounding, suggesting that PLC causes Ca2+ overload. In conclusion, activation of PLC may play a role in arrhythmias and cell injury during ischemia/reperfusion. The increase in [Ca2+]i during ischemia/reperfusion may activate phospholipase, which would further increase [Ca2+]i to form a vicious cycle.
- Published
- 1992