Involvement of the kinin system in the insulin-induced inhibition of carrageenin oedema in rats.

The carrageenin-induced foot oedema in rats is considerably decreased by insulin pretreatment, but increased in alloxan diabetes. Maximum inhibition by insulin occurs in the early phase of the oedema reaction and the insulin action is even further increased when it is administered 30 min after carrageenin. Doses of insulin as low as 1 U/kg intravenously produce significant inhibition. Determinations of the components of the kinin system indicate that the kininogenase activity is increased, and both the kininogen and kininase content are in turn decreased in the plasma of insulin-treated animals. When the carrageenin-induced oedema fluid of the paw after insulin is analysed for kininogen and kininase, their levels are significantly decreased when compared with those of oedema fluid without insulin. Histamine content in the oedema fluid is significantly enhanced by insulin. The anti-inflammatory effect of insulin under these conditions therefore appears to involve changes in the kinin system.