Ultrastructural and hormonal metabolic studies of rat liver maintained in vitro by perfusion at 30° C and 37O C: a time course study by TEM, SEM and RIA

Abstract

Isolated rat liver perfusion system has been extensively used for metabolic and functional studies. Results derived from the application of this system may reflect true biochemical changes but they may also be associated with some structural changes. This study was undertaken to correlate the cytological changes and functional integrity of isolated rat liver perfused in vitro at normal physiological temperature (37°C) and 30°C, using a non-recirculating system. The livers were perfused for 3 hours with modified Ham's F10 culture medium supplemented with thyroxine hormone (T4). The hepatocyte structural integrity was studied by light microscopy, transmission and scanning electron microscopy. The triiodothyronine (T3) and T4 hormones in the perfusion medium and the effluent fractions were assessed by radioimmunoassay. The livers perfused at 30°C remained morphologically intact at the ultrastructural level for 3 hours whilst at 37"C, hepatocytes in the centrilobular zone exhibited marked structural alterations. The percentage of T4 uptake was significantly higher (P < 0.01) in livers perfused at 30°C (50.8 * 7.7% vs 38 * 7.7%, 37"C), but the net T3 output (3.16 * 1.04 pg) and the conversion of T4 to T3 (4 * 0.62%) were significantly higher (P < 0.001) in livers perfused at 37°C in comparison to livers perfused at 30°C (1.61 * 0.84 pg and 1.68 2 0.76%, respectively). In conclusion, at 30°C the hepatic T4 uptake is not inhibited, but the rate of T4 to T3 conversion has decreased, additionally the livers remain morphologically well preserved throughout the experimental period. At 37"C, although T4 to T3 conversion is higher, structurally the livers could not be maintained intact for more than 2 hours. Therefore, isolated rat livers perfused in vitro at 30°C offer the best compromise for further morphological and metabolic studies.