Comparison of purified human and procine ACTH in man.

Abstract

The maximal rise in plasma cortisol in human subjects is equal when either human or porcine ACTH is infused in equimolar amounts. However, the data suggest that the porcine material elicits a more rapid response than the human peptide but that the human preparation remains biologically active in vivo for a longer period of time. The plasma cortisol remained elevated longer and urinary 17-hydroxycorticosteroid excretion was greater with human than with porcine ACTH. Biological assays of the fractionated 5-hr plasma pools showed that 82% of the ACTH biological activity of the human ACTH plasma pool was associated with a high molecular weight fraction in contrast to 31% of the biological activity of the porcine ACTH plasma pool. Eighteen per cent of the extracted ACTH activity from the human ACTH infusion pool had the same elution volume as standard ACTH on Sephadex G-50 as compared with 69% of the extracted ACTH from the porcine ACTH infusion pool. These data raise the possibility of a greater binding affinity of human ACTH to protein, which could account for the longer biological effect in vivo. Additional preparations should be tested before any major significance can be attached to this observation.