Proteins released from liver after ischaemia induced an elevation of heart resistance against ischaemia-reperfusion injury: 1. Beneficial effect of protein fraction isolated from perfusate after ischaemia and reperfusion of liver.

OBJECTIVES Numerous mechanisms have been proposed to participate in adaptation of heart to ischaemia by ischaemic preconditioning. We have described previously a release of cardio-protective protein fraction during ischaemic preconditioning of dog heart. In the current study the effect of high soluble protein fraction (HS fraction) released from isolated perfused rat liver after ischaemia and reperfusion was examined on isolated perfused rat heart during ischaemia-reperfusion injury. METHODS Livers were subjected to 30 or 60 min ischaemia followed with 120 min reperfusion. HS fraction was isolated using ammonium sulphate precipitation and dissolved in perfusion solution before Langendorf perfusion of isolated rat hearts. The protein pattern of HS fraction was detected with SDS-PAGE and western blot with ConA and anti ConA antibody. Hearts were then subjected to 20 min ischaemia followed by 20 min reperfusion. During reperfusion, the haemodynamic parameters of hearts were measured. Heart levels of adenine nucleotide were measured in HClO4 extracts using HPLC on C18 column. RESULTS Liver ischaemia induced changes in protein pattern of HS fraction released from the liver during reperfusion period. Particularly, we registered an increase in amount of several low-molecular weight proteins and decreased amount of high-molecular weight proteins. Proteins in this fraction isolated from perfusate after liver ischaemia interact with ConA with lower intensity as proteins isolated from perfusate after control non-ischaemic condition. HS fraction isolated from perfusate after ischaemia and reperfusion of liver had beneficial effect on heart function during 20 min ischaemia and subsequent 20 min reperfusion, documented by: i) decrease of arrhythmia score from 2 to 1 in 5 min of reperfusion and from 2 to 0 in 10 min of reperfusion; ii) improved heart contractility monitored as stabilised [dP/dt]max and increased Q parameter; iii) increased coronary flow. Proteins isolated from liver perfused under control non-ischaemic condition did not induce similar effects. The stabilisation of heart haemodynamics, observed after administration of HS proteins isolated from perfusate after ischaemia and reperfusion was associated with slight increase in ATP and ADP levels as well as decrease in AMP level.