The effect of coronary artery occlusion and reperfusion on the activities of triglyceride lipase and glycerol 3-phosphate acyl transferase in the isolated perfused rat heart.

Glycerol 3-phosphate acyltransferase (GPAT) and Triglyceride lipase (TGL) were measured in homogenates from non-ischaemic and ischaemic tissue from the isolated perfused rat heart. Ischaemia was produced by occlusion of the left descending coronary artery for 10 min. Compared to activities measured in tissue from normally perfused hearts, GPAT activity measured in tissue from the ischaemic area was considerably reduced. TGL activity in the ischaemic area was markedly increased compared to activity measured in normally perfused hearts. No change was seen in GPAT or TGL activity measured in tissue from the non-ischaemic area. The change in activities produced by ischaemia were prevented by pre-perfusion with the cardio-selective beta-antagonist Atenolol. Reperfusion of the ischaemic area resulted in TGL activity returning to the value measured in tissue from normally perfused hearts. However, GPAT activity, after 1 min of reperfusion, fell to a value lower than after 10 min ischaemia. The reperfusion-induced fall in GPAT activity was prevented by pre-perfusion with the alpha 1 antagonist Doxasozin. Pre-perfusion of the alpha 2 antagonist Yohimbine resulted in a prolongation of the increased TGL activity in the ischaemic area during reperfusion. All changes in enzyme activities were prevented by injection of 6 OH-dopamine 24 h before hearts were removed. These changes in enzyme activities show that during ischaemia there is an increased beta-adrenergic drive. On reperfusion the beta-adrenergic drive is removed but an alpha 1 adrenergic drive becomes apparent.