Effect of glucagon antibodies on plasma glucose, insulin and somatostatin in the fasting and fed rat

Abstract

A potent high-titre glucagon antibody pool was used to induce a state of acute glucagon deficiency in order to investigate the importance of glucagon in maintaining euglycaemia in the fed and fasted anaesthetised rat. Binding characteristics of the antiserum and evidence of its neutralisation of the biological effects of exogenous glucagon are described. The amount of antibody administered was capable of neutralising up to 12 times the total content of glucagon (approximately 1 nmol) in the rat pancreas. The hyperglycaemic response to 1.43 nmol exogenous glucagon was significantly inhibited in the rat by glucagon antibodies given intravenously or intraperitoneally (p less than 0.001). However, no changes in plasma glucose occurred in rats fasted 16 h (4.35 +/- 0.1 mmol/l or 24 h (4.0 +/- 0.05 mmol/l) after antibody administration. The same dose of glucagon antibodies produced no change in plasma glucose (6.1 +/- 0.2 mmol/l), immunoreactive insulin (1.85 +/- 0.05 microgram/l) or immunoreactive somatostatin (110 +/- 30 ng/l) in rats after antibody administration. Antibody excess, equivalent to a binding capacity for glucagon of 40 nmol/l in the plasma of recipient animals, was demonstrable at all times after passive immunisation. The absence of any affect on glucose concentrations following immunoneutralisation of glucagon suggests that glucagon secretion may not be a major factor in the maintenance of euglycaemia in the rat.

Immunoneutralization of endogenous glucagon with monoclonal glucagon antibody normalizes hyperglycaemia in moderately streptozotocin-diabetic rats

“…Concentrations of free glucagon after Glu-mAb treatment were not measured in this study, but results from similar experiments with polyclonal glucagon antisera containing mixtures of clones with equal or lower affinities than Glu-mAb indicate that the plasma concentration of free and thereby active glucagon should be very low [28]. In agreement with our assumption that most of the endogenous glucagon was efficiently neutralized by Glu-mAb we found that immunoneutralization of exogenous glucagon caused blood glucose levels to fall below the initial value, a result which could not be demonstrated in similar experiments with polyclonal antisera [28,39,40].…”

Glucagon and regulation of glucose metabolism

“…Conversely, there is ample evidence demonstrating that inhibition of glucagon signaling in vivo leads to a reduction in plasma glucose, or hypoglycemia. It was shown that administration of polyclonal glucagon-neutralizing antibodies abolished the hyperglycemic response to exogenous glucagon in animals (83). A similar observation was made using a high-affinity monoclonal anti-glucagon antibody (11).…”

A Comparison of the Effects of Oral and Intravenous Glucose Administration on Renal Calcium Excretion in the Rat

“…Insulin-binding reagent was obtained from Wellcome Research Laboratories, Beckenham, Kent; intra-and interassay variations were 133 and 146% respectively. Pancreatic glucagon concentrations were also estimated on large plasma samples by radioimmunoassay as previously described (Tan, Tsiolakis & Marks, 1985). Glucagon antiserum was obtained from Guildhay Antisera, Guildford, Surrey; intra-and interassay variations were 7-3 and 15-2 % respectively.…”