Fructose 2,6-bisphosphate, sugar phosphates and adenine nucleotides in the regulation of glucose metabolism in the lactating rat mammary gland.

Fructose 2,6-bisphosphate is present in the rat mammary gland, rising from a value of 1.4 nmol/g in pregnancy to 4.3 nmol/g tissue at 14 days lactation; the equivalent values calculated/ml intracellular water are 5.2 and 11.6 nmol, respectively. The tissue content of fructose 6-phosphate, fructose 1,6-bisphosphate, ATP and phosphoenolpyruvate remain relatively constant in the transition from pregnancy to the height of lactation. The changes in AMP, cyclic AMP, and citrate content of the mammary gland during lactation are such as to promote an increase in fructose 2,6-bisphosphate formation and flux through phosphofructokinase.