Eingegangen am 10. Dezember 1968
Experimentag investigations of the hypoglycaemic action of bovine proinsulin Summary. Proinsulln obtained from bovine insulin (Sc~Mn)T and A~ENS [6]) lowered the blood sugar level of rats and mice. The activity ratio proinsulin : insulin was 1 : 4 in fed rats and fasted mice, and 1 : 2 in fasted rats, based on an equimolar dosage and measuring the effect in terms of maximum lowering of the blood sugar value. After proinsulin the decrease of the blood sugar was more protracted than after insulin. Proinsulin which was incubated with trypsin in vitro, resembled insulin in degree and onset of action. In pancreateetomized, nephrectomized and two-thirds hepatectom~zed rats proinsulin acted as in normal animals. Alloxan-diabetic mice responded to proinsulin like intact mice. The reason why the onset of the hypoglyeaemic action of proinsulin was delayed is probably due to the fact that the active insulin must first be produced by a time-dependent proteolytic process. This may also be the cause of the ineffectiveness of proinsulin in the mouse convulsion test which was quoted by .