Effect of MCI-154, a calcium sensitizer, on calcium sensitivity of myocardial contractile system in endotoxemic rats.
OBJECTIVE
To investigate the effect of MCI-154 on calcium sensitivity of myocardial contractile system in endotoxemic rats.


METHODS
Skinned right ventricular papillary muscles from endotoxemic rats were prepared by saponin 500 mg/L. Forces of the skinned muscles were recorded when they were activated sequentially by different concentrations of Ca2+ with or without cardiotonic agents. The tension-pCa relationship and pCa50 of the skinned fibers were taken as the index of Ca2+ sensitivity of myocardial contractile system.


RESULTS
The maximal Ca(2+)-activated tension (Tmax) was lower, and pCa50 was reduced in endotoxemia group as compared with those in sham control group. Milrinone 50 mumol/L could not counteract the above abnormalities. However, after MCI-154 10 mumol/L was added, the Tmax and pCa50 were increased to an extent similar to that of sham control group and significantly higher than those of endotoxemia group and endotoxemia + milrinone group. Furthermore, such effects of MCI-154 were concentration-dependent.


CONCLUSIONS
The Ca2+ sensitivity of cardiac contractile system in endotoxemic rats is decreased. MCI-154 can reverse the decreased sensitivity and increase Tmax of myocardial muscles from endotoxemic rats.
Mei
J M
JM
Research Institute of Surgery, Daping Hospital, Third Military Medical University, Chongqing 400042, China.
Hu
D Y
DY
Chen
H S
HS
Liu
L M
LM
Xiao
N
N
Chen
H H
HH
Lu
R Q
RQ
D000818:Animals; D002118:Calcium / Q000502:physiology; D002316:Cardiotonic Agents / Q000494:pharmacology*; D004731:Endotoxins; D005260:Female; D066298:In Vitro Techniques; D008297:Male; D009200:Myocardial Contraction / Q000187:drug effects*; D010210:Papillary Muscles / Q000503:physiopathology; D011724:Pyridazines / Q000494:pharmacology*; D011897:Random Allocation; D051381:Rats; D017208:Rats, Wistar; D012772:Shock, Septic / Q000139:chemically induced / Q000503:physiopathology*
D002316:Cardiotonic Agents; D004731:Endotoxins; D011724:Pyridazines; C052228:MCI 154; D002118:Calcium