[Degradation and association of glucagon by intact human erythrocytes]

To extend the knowledge about systemic glucagon metabolism, intact human erythrocytes were tested for association and degradation of glucagon. When erythrocytes were incubated at 37 degrees C in 0.15 M NaCl solution, glucagon and 125I-glucagon were degraded, depending both on time and hematocrit. At a hematocrit of 0.45, about 20% of 1 nM initial glucagon were degraded during 4 h of incubation. Furthermore, cellular association of glucagon took place amounting to about 10% of the initial glucagon. Nearly 3% of the initial glucagon, but 40% of the cell-associated hormone were found to consist of intracellularly accumulated glucagon degradation products. Despite of nondetectable hemolysis after 60 min of incubation at 37 degrees C, a glucagon-degrading activity was eluted from the cells into the medium. This degrading activity was quantitatively inhibited by Contrykal, EDTA, and o-phenanthroline. Both glucagon degradation and association by human red cells were quantitatively inhibited by bacitracin. These results provided evidence for a participation of human erythrocytes in glucagon metabolism in vitro.