Abstract
Summary
Substance P. prepared from horse's intestine, is rich in a component which is highly active in releasing ACTH from pituitary glands in vitro. This factor is not P itself but is an accompanying material of unknown nature which can be separated from P by strong acid hydrolysis and shown to contain all of the ACTH-releasing activity. The hydrolysate also contains a potent histamine-like substance the activity of which, unlike that of P, is readily abolished by pyribenzamine. The releasing factor, provisionally designated as P1, is apparently identical with the ACTH-releasing agent known to occur in commercial pitressin.
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