Urea synthesis in freshly isolated and in cultured periportal and perivenous hepatocytes.

Periportal hepatocytes isolated by digitonin/collagenase perfusion produced urea faster than did similarly prepared perivenous hepatocytes, in both the presence and the absence of amino acids and various urea precursors. There was no difference between the two cell types in rates of intracellular proteolysis. The initial difference in urea synthesis persisted for 5 days during primary culture, but then gradually disappeared. Our results demonstrate that the periportal dominance of urea formation is unrelated to the currently existing acinar microenvironment in the intact liver, but probably reflects differences in acinar key enzyme activities only slowly converging during culture.