REDUCTION IN THE CA-2+-INDUCED CA-2+ RELEASE FROM CANINE CARDIAC SARCOPLASMIC-RETICULUM FOLLOWING ENDOTOXIN ADMINISTRATION

Effects of endotoxin administration on the Ca2+-induced Ca2+ release from canine cardiac sarcoplasmic reticulum (SR) were studied. Results show that the Ca2+-induced Ca2+ release from either passively or actively loaded SR vesicles was decreased by 28 to 46% (p<0.05) 4 h after endotoxin administration. Kinetic analysis reveals that the Vmax for Ca2+ was decreased significantly without changing the S0.5 and the Hill coefficient values. The binding of [3H] ryanodine to cardiac SR was reduced by 25.3% (p<0.01) following endotoxin administration. These data demonstrate that the Ca2+-induced Ca2+ release via the ryanodine-sensitive Ca2+ channel in canine cardiac SR was reduced during endotoxin shock. A reduction in the SR Ca2+-induced Ca2+ release may have a pathophysiological significance in contributing to the development of myocardial depression during endotoxin shock. © 1991.