Effects of pH and temperature on myocardial calcium-activation in Pterygoplichthys (catfish).
Fish are chronically exposed to a wide range of temperatures and acidic environments. Fish hearts have to therefore adapt to these changes in order to maintain contractility. Myofibrillar responsiveness to Ca2+ is exquisitely sensitive to both temperature and pH in mammalian myocardium. To evaluate myofilament calcium-activation, we chemically skinned ventricular myocardium from catfish (Pterygoplichthys). A decrease in pH from 7.5 to 6.8, irrespective of temperature change, shifted the calcium-force curve towards higher calcium concentrations without affecting maximal Ca(2+)-activated force. The contractile elements are therefore sensitive to changes in pH. In intact muscle preparations the active twitch force was decreased with increasing temperature (10-22 degrees C). However, the sensitivity of the myofilaments to Ca2+ was independent of temperature. These data suggest a possible role of the sarcoplasmic reticulum (SR) in mediating the effects of temperature. The response of intact muscle preparations to changes in temperature is therefore not likely due to temperature-dependent changes in myofilament calcium responsiveness.
Meadows
K N
KN
Integrated Physiology Research Laboratories, University School of Medicine, Boston, Massachusetts, USA.
Hajjar
R J
RJ
Gwathmey
J K
JK
D008841:Actin Cytoskeleton / Q000187:drug effects / Q000502:physiology; D000251:Adenosine Triphosphatases / Q000378:metabolism; D000818:Animals; D002118:Calcium / Q000378:metabolism / Q000494:pharmacology*; D002397:Catfishes / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D066298:In Vitro Techniques; D007700:Kinetics; D009200:Myocardial Contraction / Q000187:drug effects* / Q000502:physiology; D009206:Myocardium / Q000378:metabolism; D012519:Sarcoplasmic Reticulum / Q000187:drug effects / Q000502:physiology; D013696:Temperature
D000251:Adenosine Triphosphatases; D002118:Calcium