Isolated hepatocytes obtained by collagenase perfusion of adult rat livers were seeded on collagen gels and kept in a chemically defined culture medium (except for the first 6 h of culture where 10% fetal calf serum was added). Cells adopted an epitheloid shape within 4 h and arranged themselves in a trabeculae-like pattern during the first 20 h of culture. In the electron microscope numerous tight junctions and bile capillaries were observed at sites of cell-to-cell contact. From metabolite analyses in the culture medium the following conclusions can be drawn: The cells continued to synthesize urea and ketone bodies for 5 days of culture. The cytosolic and mitochondrial redox states of the nicotinamide adenine nucleotide system were as in the liver in vivo and the oxygen supply of hepatocytes was sufficient under the culture conditions. Maximal velocities of ketogenesis from octanoate and of urea formation from ornithine plus ammonium chloride were stable during a 120 h culture period and compared well with rates found in the isolated perfused rat liver.

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This report deals with the controversial problem whether bile acids exert a direct inhibitory effect on the rate of hepatic cholesterol synthesis. For this purpose rats have been provided with an ‘extracorporeal bile duct′, an experimental model which makes it possible to initiate a bile fistula two weeks after last surgery. In the animals that had recovered completely from operative trauma, a 6‐h infusion of 33.4 μmol sodium taurocholate × (100 g body weight)‐1× h−1, prevented the threefold rise of hepatic cholesterol synthesis following bile diversion. The rate of cholesterol synthesis was monitored by incorporation of [14C] acetate in vitro. There was no difference whether the animals were infused from 4–10 h (dark/light transition) or from 16–22 h (light/dark transition) besides the fact that taurocholate caused a more extensive inhibition during the light‐dark transition. A parallel kind of response was observed for the activity of hepatic 3‐hydroxy‐3‐methylglutaryl‐CoA rcductase (EC 1.1.1.34), the regulatory enzyme of cholesterol synthesis. A twofold rise of hepatic fatty acid synthesis was observed following bile diversion which was not seen in case of simultaneous bile salt infusion. It is concluded that bile salts exert direct feedback inhibition of hepatic cholesterol synthesis and that opposite results reported by other investigators are probably due to the infusion of too low doses of taurocholate.

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