Partial Purification and Characterization of Smooth Muscle Relaxant Extracted from the Slime Mold Physarum Polycephalum

Abstract

Background and Aims : Vasculature of plasmodia of Physarum polycephalum exhibits the repeated cycles of contraction and relaxation. By the analogy of smooth muscle which shows the cycles, I speculated the presence of vasodilator (s), and/or vasoconstrictor (s) in the plasmodia and tried to extract active principle (s).Materials and Methods : The extract partially purified from the plasmodia was applied to rabbit femoral artery and guinea pig ileum. The mode of effect was analyzed by measuring tension of intact and demembranated smooth muscle cells and by measuring phosphorylation of 20- kDa myosin light chain (MLCK20).Results : The extract relaxed the smooth muscles in a dose-dependant manner. The active principle is shown to be resistant to hydrolysis by acid and alkaline and to have a low molecular weight. The relaxation effect on the intact cells was absent with the demembranated cells. The relaxing was not associated with the change in MLC20 phosphorylation.Conclusion : I obtained a crude extract from plasmodia which relaxes smooth muscle. The mode of relaxing is discussed with special reference to the development a vasodilatory drug with a new mode of action.