Induction of fructose 1,6-bisphosphatase and glucose 6-phosphatase by dibutyryl cyclic adenosine monophosphate in fetal mouse liver.

Abstract

In fetal mouse liver fragments maintained in organ culture, the activities of fructose 1,6-bisphosphatase and glucose 6-phosphatase are elevated in the presence of dibutyryl adenosine 3',5'-monophosphate (Bt2-cAMP). Isobutyl-1-methylxanthine at 2.5 mM increased the two enzyme activities. The enzyme activities returned to the normal levels following removal of Bt2-cAMP from the culture medium. Glucagon at concentrations from 10(-11) M to 10(-6) M induced both enzyme activities. The developmental increases in the two gluconeogenic enzymes are supported by cyclic AMP elevated by glucagon. Only at unphysiologically high concentrations did prostaglandin-E1 show weak stimulatory effects. alpha-Adreno-agonists did not stimulate the enzyme activities. Actinomycin D and cycloheximide reduced the enzyme activities stimulated by Bt2-cAMP. Both inhibitors and removal of Bt2-cAMP prevented the incorporation of [3H]leucine into the bisphosphatase. The kinetic properties, subunit-size, and antigenic nature of the bisphosphate showed that the type of enzyme induced by Bt2-cAMP in vitro is identical to the adult liver type. The results are interpreted as indicating that cyclic AMP acts at certain sites in the syntheses of these two gluconeogenic enzymes in the fetal mouse liver.