Insulin stimulus of leucine incorporation in rat liver protein

¹ Department of Physiology, University of Chicago, Chicago, Illinois

Slices were prepared from livers of partially pancreatectomized rats and incubated 2 hr in Krebs bicarbonate solution at 37 C. Incorporation of leucine-1-C¹⁴ into protein decreased progressively as severity of diabetes increased during 1–6 months after operation; at 2–4 months insulin (0.01 U/ml of medium) plus glucose (200 mg/100 ml) added in vitro stimulated incorporation 62–78%; stimulation was not significant at 6 months. Neither insulin nor glucose was effective separately. Alkali-inactivated insulin was ineffective, even with glucose. Liver slices from sham-operated rats responded similarly to insulin under the present experimental conditions, although the maximum percentage stimulation was smaller than in the partially pancreatectomized series. It is concluded that insulin can act directly on the liver to stimulate amino acid incorporation in protein by a mechanism dependent on the presence of glucose.