The formation of peptides with uterine activity from ovine, human and bovine growth hormones and from bovine and ovine lactogenic hormones.

1. Both starch gel and disk electrophoresis demonstrated stepwise degradation of acidic preparations of human and bovine growth hormones and of ovine and bovine lactogenic hormones in solution at pH 9.0-10.0. This developed in 1-3 weeks in refrigerated solutions and in 5-16 hr on incubation at 37 degrees C. Increasing acidity accompanied degradation.2. Oxytocic activity, initially absent, developed in these same solutions of hormones during stepwise degradation and appeared to be associated with a single phase of degradation.3. Storage in solution at pH 9.5 generated oxytocic activity in an initially basic preparation of ovine growth hormone. The uterine action was attributable to a small amount of acidic material with electrophoretic properties very similar to those of the oxytocic fractions formed during stepwise degradation of the acidic preparations of growth and lactogenic hormones.4. Prolonged storage of all these hormones at pH 9.0-10.0 resulted in the formation of acidic substances of low molecular weight which ran close to the buffer front and were dialysable (14 hr) through membranes which permitted the passage of nonapeptides in 6-8 hr.5. alpha-Chymotrypsin very rapidly generated uterine stimulant action in freshly prepared solutions of human growth and bovine lactogenic hormones at pH 9.5.6. All the hormone samples used proved capable of hydrolysing purified ox haemoglobin, urea-denatured, at pH 9.5.