ACTH release by purified hypothalamic CRF preparation as assayed by intrapituitary microinjection.

ACTH-releasing potency of a purified hypothalamic CRF of pig origin was examined by use of the intrapituitary microinjection method. A good log doseresponse relationship was obtained in the dosage range from 12.5 to 50 ng injected per one anterior pituitary lobe. Two dose factorial analysis showed that the difference in response between purified CRF and median eminence extract of the rat at corresponding dosage levels was not significant and that parallelism was well maintained with a highly significant combined slope. Relative potency of the median eminence extract was calculated to be 102%. From these findings it was estimated that the median eminence of the rat would contain the CRF of the order of 600 ng.