DEPRESSOR SUBSTANCES IN THE POSTERIOR LOBE OF THE PITUITARY

¹ From the Department of Pharmacology, Temple University School of Medicine, Philadelphia, Pennsylvania

Fresh posterior pituitary lobes of cattle were extracted with acetone, the acetone evaporated to form extract X and the residual lobes dried to form powder A. Solutions of A and X, injected into cats tolerant to the pressor principle of pituitary extract, produced a fall in blood pressure and changes in organ volume. Assays as well as chemical and physiological characteristics indicate that the major portion of the activity is due to histamine.

When powder A was extracted for 20 hours with ethyl alcohol the residual powder is known as B and the alcoholic extract after evaporation is known as Y. Solutions of B or Y, injected into cats tolerant to the pressor principle of pituitary extract, produced a fall in blood pressure. If the extraction were continued for 80 hours, a residual powder C was produced which may contain slight traces of depressor substances, but usually all of the depressor material is present in the extract Z. Assays, as well as chemical and physiological characteristics, indicate that most of the activity of Y is due to histamine.

When enough ethyl alcohol is added to an acid extract of posterior lobe pituitary powder (A) to make 70 per cent alcohol, a precipitate is formed. Solutions of this precipitate (D), the pressor principle (E) or oxytocic principle (F) injected into cats tolerant to the pressor principle of pituitary extract, did not produce any change in blood pressure or organ volume.