The effect of thapsigargin on sarcoplasmic reticulum Ca2+ content and contractions of single myocytes of rat ventricular myocardium.
The effect of Thapsigargin (TG) shown to block selectively the Ca(2+)-ATPase of sarcoplasmic reticulum (SR) on the SR Ca2+ content and contractions of single rat cadiomyocytes was investigated. In 80% of cells 10(-6) M TG blocked Ca2+ uptake by SR at rest, depleted the SR Ca2+, inhibited postrest potentiation and changed the pattern of response to premature contractions. Amplitude of steady state contractions was reduced to 11 +/- 4% of pre-TG control. In 20% of cells TG had similar effect on the SR function, however, amplitude of contractions was reduced to only 50 +/- 7% of control. It is concluded that the results obtained in 80% of the cells are compatible with the wide-spread notion that contractions of rat cardiac myocytes are activated predominantly by Ca2+ released from SR. However, population of myocytes of ventricular myocardium of this species is not homogeneous in this respect. In 20% of them contractions are activated by both sarcolemmal and SR Ca2+ contribution being approximately equal. These cells occupy intermediate position between guinea-pig cells and the bulk of rat cells.
Lewartowski
B
B
Department of Clinical Physiology, Medical Centre of Postgraduate Education, Warsaw, Poland.
Wolska
B
B
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D006352:Heart Ventricles / Q000166:cytology / Q000187:drug effects*; D006636:Histamine Release / Q000187:drug effects; D066298:In Vitro Techniques; D009200:Myocardial Contraction / Q000187:drug effects*; D010936:Plant Extracts; D010946:Plants, Medicinal; D051381:Rats; D012519:Sarcoplasmic Reticulum / Q000187:drug effects*; D013729:Terpenes / Q000494:pharmacology*; D019284:Thapsigargin
D010936:Plant Extracts; D013729:Terpenes; D019284:Thapsigargin; D002118:Calcium