EFFECTS OF A TOXIN FROM THE MUCUS OF THE CARIBBEAN SEA-ANEMONE (BUNODOSOMA-GRANULIFERA) ON THE IONIC CURRENTS OF SINGLE VENTRICULAR MAMMALIAN CARDIOMYOCYTES

The effects were studied of a toxin (Bainh) isolated from the secretio n of the Caribbean sea anemone Bunodosoma granulifera on electrical an d mechanical activities of rat ventricular muscle. The effects on the ionic currents of single rat and dog ventricular cardiomyocytes were s tudied using the whole-cell recording patch-clamp technique. In the co ncentration range from 1 to 10 mg/ml, Bainh increased the force of con traction and induced an increase in action potential duration of ventr icular multicellular preparations. In single cardiomyocytes, at concen trations up to 10 mg/ml Bainh showed no significant effects on the sod ium current. However, at 0.5-1 mg/ml it increased the L-type Ca curren t (I-CaL) by 25-50%. This increase in I-CaL was not voltage dependent and was reversible after washout. The transient outward current was no t significantly affected by Bainh (1-10 mg/ml). In this concentration range, Bainh markedly (approximate to 75%) increased the inward-going rectifier current, I-K1. This effect that was not voltage dependent an d was fully reversible upon returning to control solution. It is sugge sted that these effects on ionic currents could explain the positive i notropic action of Bainh on cardiac multicellular preparations. (C) 19 97 Elsevier Science Ltd.