Effects of Recombinant Toxin Phospholipase D in Cardiac Muscle of Rats

Abstract

Loxoceles spiders gender are worldwide spread and its bites can cause dermonecrosis or even a systemic effect (hemolysis, kidney and liver injury). It is believed that phospholipase D, the main component present in the venom, could be responsible for the injury. In this study, we used a recombinant form of phospholipase D (rLiD1) and evaluated its direct and systemic effects on the contractility of papillary muscles and in the left intra ventricular pressure of isolated perfused hearts, respectively. In papillary muscle directly exposed to rLiD1 no effects on force, maximum speed of contraction (df/dt max ) or relaxation (df/dt min ) were observed. In isolated perfused heart, the peak of systolic pressure and the rate of relaxation (dP/dt min ) were reduced in animals treated with rLiD1. However, the maximum speed of pressure developed during contraction (dP/dt max ) was unaffected. These data suggest that rLiD1 did not affect directly the excitation contraction coupling or the contractility of the myocardium but its systemic effect can induce reduction in the cardiac performance.