It has been suggested that glucagon-like immunoreactivity (GLI) of gastrointestinal tissues might, like pancreatic glucagon, have calcium-lowering activity. Studies were designed, therefore, to determine if calcium absorption was associated with GLI release from the gut. The intraduodenal administration of 4.5 mmoles of calcium chloride per kg of body weight to conscious dogs was associated with a prompt rise in plasma GLI from a base line of 2.2 ng/ml (SEM ±0.2) to a peak of 4.3 ng/ml (SEM ±0.3) at 45 and 60 min, in association with a rise of plasma calcium from 8.6 to 10.4 mg/100 ml. Neither pancreatic glucagon, insulin, nor glucose changed. Smaller calcium loads had progressively diminishing effects on GLI release. Calcium lactate also appeared to stimulate effectively GLI release. Both magnesium chloride and sodium chloride given intraduodenally were associated with a significant though modest increase in GLI.
Ingolf Böttger, Gerald R. Faloona, Roger H. Unger