Minimal protection of the liver by ischemic preconditioning in pigs

Ischemic preconditioning (IP) protects the rat liver. In pigs, in which hepatic tolerance to ischemia is similar to that in humans, information on IP is lacking. Therefore, in enflurane-anesthetized pigs, hepatic vessels were occluded for 120 min (protocol 1) or 200 min (protocol 2) without (control) and with IP (3 times 10 min ischemia-reperfusion each). In protocol 1, cumulative bile flow (CBF) during reperfusion was greater in IP (47.3 +/- 5.2 ml/8 h) than in control (17.1 +/- 7.8 ml/8 h, P < 0.05). ATP content tended to recover toward normal during reperfusion in IP, whereas it remained at ischemic levels in control. Serum enzyme concentrations increased similarly during reperfusion, and <1% hepatocytes were necrotic or stained terminal deosynucleotidyl transferase-mediated dUTP nick-end labeling-positive in control and IP groups. In protocol 2, no differences in CBF, ATP, or serum enzyme concentrations during reperfusion were measured between control and IP groups, except for a somewhat reduced lactate dehydrogenase in IP. The number of necrotic or terminal deosynucleotidyl transferase-mediated dUTP nick-end labeling-positive hepatocytes tended to be greater in the IP than the control group. Thus IP provides some functional protection against reversible ischemia but no protection during prolonged ischemia in pigs.