Establishment of a clonal strain of hepatoma cells which maintain in culture the five enzymes of the urea cycle

A clonal strain of epithelial cells has been established from the transplantable Morris hepatoma 7800 and is designated 7800C1. The cells grow with a population doubling time of about three days in serum‐supplemented synthetic medium. Cells of the 7800C1 strain have maintained measurable activities of all the enzymes of the urea cycle during 17 months in continuous culture. The activity of argininosuccinate lyase is approximately that found in normal rat liver, while argininosuccinate synthetase, carbamoyl phosphate synthetase, arginase and ornithine carbamoyl transferase activities are, respectively, 40%, 28%, 6%. and 1% of normal values. Treatment of 7800C1 cells with glucagon, dibutyryl 3′,5′‐cyclic adenosine monophosphate or hydrocortisone did not increase the activity of any of the five enzymes.