INHIBITION OF PAF-ACETHER EFFECTS ON ISOLATED GUINEA-PIG HEARTS BY ZINC IONS (ZN2+)

PAF-acether is a phospholipid synthesized by most animal tissues and e xerting a strong decrease on the heart's contractile force and coronar y flow. PAF-acether (10(-9) and 10(-10)M) was administered to isolated guinea pig hearts perfused via the Langendorff apparatus with Chenowe th solution. Zinc (1.5 mu M) is known to benefit heart function thus, Zn2+ (1.5, 7.5, and 30 mu M) was added in the perfusing solution befor e or after PAF-acether administration. Contractile force, coronary flo w, and heart rate were recorded by means of a Narco MK-IV Physiograph throughout all modes of perfusion. Calcium inhibitor (Verapamil 10(-10 )M) and Pb+2 Co2+ (1.5 x 10(-6)M) were used subsequently in the perfus ing solutions in order to elucidate some of the Zn and PAF interaction s observed. All hearts were analyzed for their Zn and Ca content by me ans of an Atomic Absorption Spectrophotometry (AAS). Our data suggest that low concentrations of zinc (1.5 mu M) can strongly inhibit PAF-in duced decrease of contractile force and coronary flow. Zinc-inhibiting effects on PAF's negative inotropic action (myocytic level) is not ex erted through Zn-Ca antagonism. Nevertheless, a Zn-Ca antagonism in th e arteriolar level cannot be excluded. Zinc inhibits PAF selectively o nly if it is administered before PAF injection and this strongly sugge sts a receptor interaction between the metal and the phospholipid at t he heart level.