Studies on bile secretion 1. bile secretion in perfused liver
Journal of Kyoto Prefectural University of Medicine 94(2): 183-191
Bile secretion is one of the most important functions of hepatocytes. Kinetics of bile salt uptake and secretion and analysis of bile salt dependent and non-dependent fractions of bile were studied in male Wistar rat using liver perfusion method. The uptake of taurocholate (TCA) obeyed Michaelis-Menten kinetics. The maximal uptake velocity (Vmax) and the half-saturation constant (Km) were 1.416 .mu.mol/min per g liver and 314.60 .mu.mol/l, respectively. Bile salt secretion rate increased in non-linear fashion with increasing TCA infusion rate up to 3 .mu.mol/min per 100 g body wt. Maximal secretion rate (Tm) was 180.45 .+-. 20.33 nmol/min per g liver. When bile flow was plotted against bile salt secretion rate, different regression lines were obtained according to bile salt concentration in bile. The slopes of these regression lines increased; the Y-intercepts decreased in proportion to diminishing bile salt concentration in bile. Time study of TCA uptake revealed that TCA infused at the rate below Tm was totally extracted; the uptake rate of TCA infused at the rate more than Tm decreased gradually to Tm value. Apparently, bile salt dependent bile flow is the major fraction of bile produced by hepatocytes. Bile salt dependent bile is thought to be produced heterogeneously with the hepatic lobule.