ADRENOCORTICAL ACTH RECEPTORS IN PIGS OF DIFFERING INVIVO RESPONSE TO ADRENOCORTICOTROPIN

1. Adrenocortical membrane protein was isolated from the adrenal glands of 12 Large White x Landrace male pigs, six with high adrenocortical response to adrenocorticotropic hormone (ACTH) and six with low response. 2. The peptide (Phe2, Nle4) ACTH1-24 was iodinated by the chloramine-T method and served as the radioligand in receptor binding studies, 3. Only one class of ACTH receptor was detected, with K(d) = 2.57 +/- 0.35 x 10(-9) M and B(max) = 1.59 +/- 0.06 pmol/mg protein in high responders and K(d) = 1.68 +/- 0.18 x 10(-9) M and B(max) = 1.17 +/- 0.11 pmol/mg protein in low responders. 4. The difference in the B(max) between high and low responders was significant (P < 0.05), the difference in K(d) was not statistically significant.