Role of insulin in the hypoglycaemic effect of sublethal Bordetella pertussis infection in mice.

Mice were infected intranasally with a sub-lethal dose of Bordetella pertussis organisms (1.2 x 10(5) colony forming units per mouse), control animals receiving the vehicle intranasally. The experiments were performed 14 days later. Serum glucose and insulin concentrations were studied across a 24 h period in freely fed animals and the changes in serum glucose and insulin concentrations in response to feeding were examined in mice fasted for 18 h. The responsiveness of mice to injected insulin (0.5 and 5.0 units/kg i.v.) was also examined. Pertussis-infected mice developed hypoglycaemia and hyperinsulinaemia relative to the controls. These changes were present across a 24 h period although the magnitude of the differences between values seen in control and infected animals varied and the hyperinsulinaemia was not seen at all times. Infected mice showed a markedly diminished hyperglycaemia and an exaggerated hyperinsulinaemia following food ingestion, relative to normal controls. Pertussis-induced hypoglycaemia was abolished following destruction of the pancreatic islet B cells with alloxan (80 mg/kg i.v.). The serum glucose response to a low dose of insulin was significantly attenuated by B. pertussis infection although the hypoglycaemia produced by a high dose was prolonged. It was concluded that B. pertussis infection-induced hypoglycaemia was secondary to hyperinsulinaemia, possibly caused by an exaggerated insulin secretory response to food intake.