Alteration in the fluorescence polarization of rat plasma and liver cell membranes following bile duct ligation in rats.

The fluorescence polarization levels of liver cell membranes and plasma were analyzed to determine membrane fluidity following bile duct ligation (BDL) in rats. Fluorescence polarization was measured with a spectrofluorophotometer equipped with polarizers, using 1,6-diphenyl-1,3,5-hexatrien (DPH) as a probe. After bile duct ligation, liver cell membrane fluidity decreased significantly for up to 14 days after surgery (P < 0.001 on 3rd and 7th days). The polarization of the plasma in rats with BDL slightly but significantly increased compared to the levels in the control animals over the 14-day period following BDL. In addition, a small but significant correlation in the polarization levels between plasma and liver cell membranes (r = 0.362, P < 0.02) was observed. The co-incubation of BDL plasma with normal liver cell membranes resulted in a decrease in membrane fluidity, which suggested that BDL rat plasma had a direct effect on membrane fluidity. After a 70% hepatectomy, the polarization of the membranes from remnant livers in the BDL rats remained elevated relative to the sham-operated controls. It is thus concluded that the membrane fluidity of the livers in BDL rats decreases following bile duct ligation and does not increase after a 70% hepatectomy, presumably due to the increased plasma level of bilirubin.