Open AccessExtracellular Calcium Modulates the Effects of Protamine on Rat Myocardium
Author(s) -
Jean-Stéphane David,
Benoît Vivien,
Yves Lecarpentier,
Pierre Coriat,
Bruno Riou
Publication year - 2001
Publication title -
anesthesia and analgesia/anesthesia and analgesia
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.404
H-Index - 201
eISSN - 1526-7598
pISSN - 0003-2999
DOI - 10.1097/00000539-200104000-00005
Subject(s) - inotrope , calcium , protamine , medicine , endocrinology , heparin , extracellular , cardiac muscle , nifedipine , chemistry , biochemistry
We studied the effects of protamine (10-300 microg. mL(-1)) as well as its interaction with heparin in rat left ventricular papillary muscles in vitro at calcium concentrations of 0.5 and 1 mM under low (isotony) and high (isometry) loads. Protamine induced a negative inotropic effect that was less pronounced at calcium 0.5 mM (active force at protamine 300 microg/mL, 84 +/- 20 vs 57 +/- 15% of baseline, P: < 0.05); whereas at calcium 1 mM there was a marked contracture of the muscle. For the smallest concentrations of protamine and at calcium 0.5 mM, we observed a moderate positive inotropic effect that was suppressed by nifedipine. Protamine induced a negative lusitropic effect under low load and decreased postrest potentiation, suggesting an impairment in the functions of the sarcoplasmic reticulum. Heparin was able to inhibit and reverse the negative inotropic effect of protamine. The negative inotropic effect of protamine is enhanced by an increase in extracellular calcium concentration. This negative inotropic effect is probably related to calcium overload and impairment in sarcoplasmic reticulum functions, and heparin can block these effects.