Abstract
Since the demonstration by Long and Evans 1 of the growth hormone of the anterior pituitary, various workers have confirmed the existence in alkaline extracts of the anterior lobes of animals of a growth-promoting substance. Van Dyke and Wallen-Lawrence 2 have suggested the use of totally hypophysectomized animals as a test object for determining the potency of extracts. The latter also made definite progress in the preparation of potent extracts which were less crude than those previously used.
We have been successful in preparing highly potent extracts of the anterior lobe of oxen. These extracts have been tested for growth-promoting effects upon totally hypophysectomized rats. Growth has started almost immediately following the institution of therapy and has continued at a fairly uniform rate (see chart).
It was first observed that an alkaline extract (anterior lobes extracted with 10 volumes of 1% NH4OH) which had been partially deproteinized, by the addition of acetic acid to pH 6.5 and filtering, had a slight growth-promoting effect in hypophysectomized rats. Such extracts were then saturated with ammonium sulphate in the presence of 1% NH4OH, and the resultant precipitate collected, extracted with dilute ammonia and dialyzed. After dialysis the solution was concentrated at low temperature and pressure. During the concentration process a semi-crystalline substance separated out at a pH of 7.5 to 8. This was removed and an alkaline extract of it was found to be highly potent in stimulating growth in hypophysectomized rats.
From these leads the following method has been evolved. The anterior lobe tissue is treated with several volumes of dilute alkali: 0.5 to 1% NaOH or 1% NH4OH.
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