CARRIER-MEDIATED LACTATE ENTRY INTO ISOLATED HEPATOCYTES FROM FED ANDSTARVED RATS - ZONAL DISTRIBUTION AND TEMPERATURE-DEPENDENCE

We examined the possibility of quantitative differences in lactate ent ry into periportal and perivenous hepatocytes under different nutritio nal states. The rate of C-14-L(+)-lactate uptake was determined after 15-second incubations with freshly isolated zonally separated hepatocy tes using a centrifuge stop technique at 37 degrees C and 4 degrees C, in the presence or absence of either differing amounts of unlabelled lactate or of a hepatocyte lactate transport inhibitor, alpha-cyano-3- hydroxycinnamate. Total entry as well as carrier mediated entry of C-1 4-L(+)-lactate into the isolated cell populations was found to be simi lar in periportal and perivenous hepatocytes, irrespective of the nutr itional state of the animal. Periportal and perivenous hepatocytes sho wed a greater tendency to transport lactate when isolated from starved animals, in agreement with previously reported data from non-zonally separated isolated hepatocytes. The activity of the hepatocyte plasma- membrane lactate transporter was diminished between fourfold and eight fold in transport studies conducted at 4 degrees C; similar results we re obtained in unseparated and zonally separated suspensions. Temperat ure dependence of the hepatocyte transporter is markedly less than tha t reported for the erythrocyte transporter.