Plasma glucagon in pups, decreased by fasting, unaffected by somatostatin or hypoglycemia

In pups less than 4 days old, the mean basal plasma immunoreactive glucagon (IRG) level was about 3 times higher than in adult dogs. This high level decreased with age, and in pups older than 12 days the mean plasma IRG level did not differ from that in adults. Insulin-induced hypoglycemia did not raise plasma IRG concentration in young pups. Fasting decreased plasma IRG in young, but not in older pups. This decrease is consistent with the decrease in gluconeogenesis and in contrast to the metabolic adjustments observed in the adult organism. In pups less than 7 days old, both the pancreas and gastric mucosa contained considerably more IRG than the normal value reported for adult dogs. Gastroduodenal IRG was immunologically indistinguishable from pancreatic glucagon. In pups, somatostatin did not decrease the plasma concentration of either IRG or immunoreactive insulin (IRI) and caused no change in plasma glucose or in the rates of glucose production and utilization calculated from experiments with tracers. The experiments indicate that in pups the pancreatic and gastric alpha-cells are unresponsive to stimuli normally effective in grown dogs.