HORMONAL-REGULATION AND EFFECTS OF GLUCOSE ON TYROSINE AMINOTRANSFERASE ACTIVITY IN ADULT RAT HEPATOCYTES CULTURED ON FLOATING COLLAGEN MEMBRANES

  • 1 January 1978
    • journal article
    • research article
    • Vol. 38  (6) , 1550-1555
Abstract
Adult rat parenchymal hepatocytes can be maintained in primary culture on floating collagen membranes for prolonged periods of time. In this system the enzyme tyrosine aminotransferase [EC 2.6.1.5] is induced by glucagon (10-6 to 10-8 M), hydrocortisone (10-5 to 10-8 M), and cyclic[c]AMP (10-4 to 10-5 M). Epinephrine (10-4 M) induces the enzyme only in the presence of hydrocortisone. Addition of actinomycin D inhibited the induction of tyrosine aminotransferase by hydrocortisone and cAMP. Maintenance of the cultured hepatocytes in the presence of glucose (3 g/l) results in partial suppression of the inducing effects of glucagon and cAMP. cGMP does not mimic the effects of glucose. The phenomenon of glucose repression of enzyme induction, demonstrated in vivo in mammalian liver, is independent of changes in levels of serum hormones, which occur in vivo as a result of glucose administration. Glucose repression is not mediated by changes in intracellular levels of cAMP and cGMP.