Effects of inorganic phosphate on calcium and tension oscillations in saponin-treated rat cardiac muscle.
The effects of inorganic phosphate (Pi) on the sarcoplasmic reticulum (s.r.) were studied in saponin-treated rat cardiac muscle. Ca2+ -uptake and release by the s.r. was detected using Indo-1. Oscillations of Ca2+ and tension occurred when the [Ca2+] of the bathing solution was around the threshold for force production. Introduction of Pi (20mM) caused a slow transient release of Ca2+ from the s.r. The oscillations were abolished in the presence of Pi. Removal of Pi caused a rapid fall in Ca2+ followed by a large transient increase in [Ca2+] and tension. Results are consistent with a phosphate-induced decrease Ca2+ available for release.
Smith
G L
GL
Institute of Physiology, University of Glasgow, Scotland.
Steele
D S
DS
Crichton
C A
CA
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D006321:Heart / Q000187:drug effects / Q000502:physiology*; D006352:Heart Ventricles; D066298:In Vitro Techniques; D007700:Kinetics; D009200:Myocardial Contraction / Q000187:drug effects*; D009206:Myocardium / Q000378:metabolism*; D010710:Phosphates / Q000494:pharmacology*; D051381:Rats; D012503:Saponins / Q000494:pharmacology; D012519:Sarcoplasmic Reticulum / Q000187:drug effects / Q000378:metabolism
D010710:Phosphates; D012503:Saponins; D002118:Calcium