Comparative activation by AMP and cyclic-AMP of rat erythrocyte and reticulocyte glycolysis

Incubation of raty erythrocytes and reticulocytes in Tris-Ringer's medium with 5 mM cyclic-AMP or AMP increased lactate formation and glucose utilization. The glycolysis-stimulating effect of cyclic-AMP is very similar to that of AMP and, in both cases, it seems to be higher in reticulocytes than in erythrocytes. 0.5 mM norepinephrine produced a much higher lactate formation in reticulocytes than in erythrocytes, suggesting a greater adenylate cyclase activity in younger cells. 300 micrometer cyclic-AMP and AMP reverse inhibition produced by ATP (up to 1.5 micrometer) on phosphofructokinase from rat reticulocyte haemolysates. Both nucleotides are positive allosteric effectors of the enzyme as shown by displacement of F6P-saturation curve to hyperbolic kinetics. Similar results were previously obtained with rat erythrocytes. This deinhibitory effect is suggested to be responsible of the above glycolysis-stimulating effect.