LIMITATIONS OF THE IN VITRO PITUITARY INCUBATION SYSTEM AS AN ASSAY FOR ACTH-RELEASING ACTIVITY
The applicability of Saffran and Schally's in vitro pituitary incubation technique to the detection of the ACTH-releasing activity of blood serum fractions, obtained from intact, stressed, adrenalectomized, and stressed–adrenalectomized donor rats, was investigated. The various fractions assayed in this system were found to be markedly active. The activity, which bore no apparent relationship to the physiological state of the donors, was related in part to inhibition of ACTH inactivation, in part to enhanced release of ACTH by the incubated pituitaries. In view of the non-specificity of the observed responses, it is suggested that the increased in vitro release of ACTH may reflect passive leakage of the hormone, as opposed to true secretory activity, and the physiological significance of findings obtained with this method is seriously questioned.