Uptake of galactose, ouabain and taurocholate into centrilobular and periportal enriched hepatocyte subpopulations

Rat hepatocytes were isolated by a collagenase perfusion technique with subsequent subfractionation on Metrizamide gradients into subpopulations which have been designated band I and band II and are likely to be enriched with centrilobular and periportal cells, respectively. Band I was found to have a higher concentration of 5'-nucleotidase and band II a higher concentration of alcohol dehydrogenase. Furthermore, pretreatment of rats with phenobarbital led to higher cytochrome P-450 in the band I (centrilobular enriched) as compared to the band II (periportal enriched) subpopulations of hepatocytes. These data support their ascribed lobular origins. The uptake of a single concentration of galactose, ouabain and taurocholate into each of the two subpopulations was investigated until the concentration within the hepatocytes no longer increased. No difference was found in the uptake of [14C]galactose (25 mM) between the two hepatocyte subpopulations. However, the uptake of [3H]ouabain (125 microM) was greater in the centrilobular as compared to periportal enriched fraction of the hepatocytes. An even greater difference was found for the uptake of [3H]taurocholate (25 microM). The kinetics of taurocholate uptake were subsequently investigated. The Km for each subpopulation was 21 microM, while the Vmax of the centrilobular enriched fraction was 2.03 and that of the periportal enriched fraction was 1.57 nmol/min/mg of protein. These results show that there is a difference in uptake into hepatocytes of centrilobular and periportal origin for ouabain and taurocholate, but not for galactose.