Isolated rat livers perfused with human serum (five experiments in each group). In the control group (perfusion with buffer solution alone), the liver flow remained stable and higher than 3 ml min−1 g−1 during the 65 min period of observation. After perfusion with 2.5, 5, 10 and 20% fresh human serum, the liver flow dropped by 23, 53, 66 and 80%, respectively. *:P<0.05 vs controls.