Failure of Synalbumin to Exhibit Insulin Antagonism in Vivo

An insulin antagonistic albumin (human fraction V) was infused over a three-hour period into lightly anesthetized rats in an unsuccessful attempt to demonstrate an in vivo effect of synalbumin. This albumin antagonist did not affect the plasma insulin concentration or the establishment of steady blood glucose levels in nonfasted normal rats or the disposal of exogenous glucose in fasted normal rats. Synalbumin also had no effect on steady-state blood sugar or the handling of exogenous glucose in animals with limited insulin reserve (partially pancreatectomized). The hypoglycemic response to exogenous insulin was not altered. In vitro experiments showed that insulin insensitivity was not induced in the diaphragms of infused rats, nor did their plasma inhibit the action of insulin on normal diaphragms. It was concluded that on the basis of available evidence synalbumin could not be classed as a physiologically active substance.