STUDIES ON INSULIN WITH PROTAMINE

¹ Connaught Laboratories, University of Toronto, Toronto, Canada

The preparation of protamine is described. Using this method three samples of protamine were prepared from the testes of cohoe salmon, spring salmon, and steelhead salmon. A method for assaying insulin with protamine on rabbits is outlined. Using this method similar sustained hypoglycaemic effects were observed when any of the three protamines or that from rainbow trout were mixed with different vials of the same lot of insulin. Using protamine and insulin of low ash content a much less prolonged insulin action was obtained. The addition of a small amount of zinc to the insulin before adding the protamine greatly sustained the hypoglycaemic action. These results suggest that zinc, or some other metal, is largely responsible for the combination that results in the prolonged hypoglycaemia produced by insulin with protamine. Further proof of this was shown by the fact that freshly mixed commercial preparations of protamine and insulin (which contained only traces of zinc) are not as effective in prolonging insulin action as are those containing a small amount of added zinc or as suspensions which have stood for 40 hours.