[Increase of 5'-nucleotidase activity in liver plasma membranes during fasting in the rat].

The effect of fasting on 5'-nucleotidase activity was assessed in microsomes and purified plasma membranes from rat liver. The microsomal 5'-nucleotidase activity (mean value: 0.062 mumol/min/mg protein at 37 degrees C in the fed rat) is increased about twice in the fasted rat (mean values: 0.11, 0.125 and 0.11 mumol/min/mg protein after 24, 48 and 72 hours of fasting, respectively). This result was further confirmed after separation of plasma membranes from the bulk of microsomial membranes by sucrose gradient centrifugation. The results are discussed with respect to the phosphatidylinositol glycan-mediated anchoring of the ectoenzyme to the cell membrane and to the putative biological effect of extracellular adenosine on the liver metabolism.