Factors affecting insulin responsiveness of triglyceride synthesis in incubated chicken hepatocytes

A technique was developed to isolate and incubate hepatocytes from 4-day-old chickens. Hepatocytes incubated in serum-free medium containing 1 ng chicken insulin/ml had greater rates of triglyceride (TG) synthesis than insulin-unexposed cells. Greater concentrations of insulin enhanced TG synthesis. Addition to medium of a supplement containing several hormones greatly improved insulin responsiveness of TG synthesis in hepatocytes compared with cells not incubated in supplemented medium. The medium supplement did not affect TG synthesis in hepatocytes incubated in the absence of insulin. The presence, compared with the absence, of triiodothyronine in the medium supplement improved insulin responsiveness of TG synthesis. In hepatocytes incubated in supplemented medium, increasing chicken insulin concentrations augmented malic enzyme activity. Hepatocytes incubated in supplemented medium containing bovine insulin had lesser rates of TG synthesis than cells incubated with similar concentrations of chicken insulin. To determine whether insulin responsiveness of TG synthesis is affected by age of chicken, hepatocytes from 4-, 11-, and 74-day-old chickens were incubated in supplemented medium. Responsiveness of TG synthesis to chicken insulin progressively decreased in hepatocytes from older chickens. Results indicate that hepatocytes isolated from 4-day-old chickens and incubated in supplemented medium are responsive to dilute insulin concentrations and may be useful to investigate the biochemical effects of this hormone.