Effect of Glucagon on Cyclic AMP, Albumin Metabolism and Incorporation of 14C‐Leucine into Proteins in Isolated Parenchymal Rat Liver Cells

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Abstract
Parenchymal rat liver cells were isolated by the collagenase method and incubated in Krebs‐Henseleit buffer containing 0.5% gelatin. The basal level of cyclic AMP in isolated cells was 0.52 nmol per g liver wet wt. Glucagon (10‐10‐ 10‐6 M) caused a significant increase in the level of cyclic AMP. Maximum levels were obtained 2–15 min after addition of glucagon. Repeated administration of glucagon caused a new increase in cyclic AMP, but the response was lesser than after the first addition of glucagon, indicating refractoriness to glucagon. The rate of albumin secretion was 4.6 μg/min per g liver wet wt. This is about the rate found in the perfused liver. Glucagon (10‐8‐ 10‐6 M) inhibited albumin secretion and the incorporation of 14C‐leucine into albumin, into total proteins in the medium and into total proteins in the cell suspension. The effect of glucagon on albumin secretion is compatible with an effect on the rate of synthesis. A positive correlation existed between the maximal level of cyclic AMP after glucagon administration and the inhibition of both albumin secretion and the incorporation of 14C‐leucine.