Abstract
This investigation was begun with the object of developing a method for the assay of extracts containing the cortical hormone which could be carried out with smaller amounts of extract than is required when bilateral adrenalectomized cats or dogs are used.
Hartman 1 has used the growth curve of treated suprarenalectomized rats of 100 to 150 gm. in weight as an alternative method of assay.
It was discovered that immature rats of the colony in this laboratory (Wistar strain) which has been inbred by us for a number of years do not survive suprarenalectomy, except in rare instances. For example, of a group of 57 from which the glands were removed at 4 weeks of age, 56 had died on the tenth day. A search of the literature did not reveal any data indicating the ability of such young rats to survive bilateral suprarenalectomy and there has been little agreement between the results of various authors concerning the survival period of suprarenalectomized adults. It seemed advisable, therefore, to investigate the possibility of using such animals for the standardization of potent extracts of the cortical hormone. The results of this study are most encouraging, and it is suggested that a rat unit be taken as the minimum daily dose of extract which will protect (for at least 20 days) 50% of a group of animals suprarenalectomized at 28 days of age, the extract being administered subcutaneously twice daily. Table I illustrates an experiment in which the potency of an extract has been demonstrated.
The extracts used at first were made according to Swingle and Plfiffner's 2 method. Later it was found that the following simplified process was satisfactory.
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