DENSITY OF MUSCARINIC RECEPTORS IN RAT MYOCARDIUM DURING EARLY SEPSIS

The muscarinic receptor changes in two subcellular fractions of rat my ocardium during sepsis, the sarcolemma (SL) and light vesicles (LV), w ere studied. [H-3]-quinuclidinyl benzilate ([H-3]-QNB) was used as a r adioligand. Sepsis was induced by cecal ligation and puncture (CLP). T he septic rats had higher pulse rates and slightly higher blood glucos e levels than control rats. The marker enzyme assays revealed that the SL fraction was enriched with 5'-nucleotidase and the Na+-K+-ATPase a ctivity increased over 20-fold, while the LV fraction showed very litt le enrichment when compared with the homogenate. [H-3]-QNB binding stu dies showed that B-max increased by 58.8% in SL with no changes in LV during early sepsis (9 h post-CLP), but there was no significant chang e in the K-d value. These data indicate that muscarinic cholinergic re ceptors in rat heart SL increase during early sepsis. Since the muscar inic cholinergic receptors mediate parasympathetic modulation of myoca rdial contractility, changes in the number of muscarinic receptors in the cardiac SL may have a pathophysiologic significance in the develop ment of hemodynamic changes during sepsis.