Abstract
No satisfactory method for the assay of cortin has been available. The survival and behavior of adrenalectomized cats is unsatisfactory as it requires too much time and too much cortin.
The white rat is more satisfactory because less cortin is required and a large number of animals may be used. The animals which do not need cortin can be ruled out by employing a sufficiently large number. Young rats (50-150 gm. weight) fail to gain weight, or even lose, after removal of both adrenals. The injection of sufficient cortin enables these animals to grow and develop normally. If the cortin is inadequate a majority fail to gain or may even lose within 1 to 3 days. This forms a basis for the test.
From observations on a considerable series of adrenalectomized rats we have developed the method which follows. Male or female white rats, of standard stock, weighing between 75 and 150 gm. are used. Both adrenals are removed through the lumbar path at one operation. They are fed a uniform standard diet and are weighed in the morning at the same time each day. When not being used for assay their growth is maintained by the injection of adequate cortin. Animals allowed to go more than a day or two without adequate cortin must be brought back to normal with cortin before they can be used for assay because more cortin is required to bring them up if they have lapsed. Injections should be made twice daily, preferably 10 to 12 hours apart because some individuals will not grow normally with one injection.
To assay, one uses 3 or more groups containing sufficient numbers to rule out individual variation. A range of doses is employed, one for each group.
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