Abstract
Summary
Rat pituitary extract and U.S.P. Reference Standard Corticotropin were compared, in Saffran and Schally's in vitro system, with respect to inactivation, corticoidogenic effects, and corticotrophic activation conferred to the incubated glands, as a result of a limited period of contact. The only difference noted pertained to the extent of this residual activation. The relative potency of pituitary extract to reference standard, determined on that basis, was observed to increase linearly with time of contact. This is ascribed to different rates of adsorption, by the glands, of the 2 corticotropins. Taken in conjunction with the more rapid inactivation and disappearance of ACTH in vivo than in vitro, differential adsorption is suggested as the basis of the discrepancy in the estimates of rat pituitary ACTH concentration, yielded by in vivo and in vitro assays.
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