Presence of corticotropin releasing factor-like immunoreactivity in hypophysial portal blood

Hypophysial protal blood was collected from pentobarbital anesthetized male rats, and the content of corticotropin releasing factor-like immunoreactivity (CRF-LI) was measured using an RIA developed for synthetic ovine CRF. The concentration of CRF-LI in portal plasma was 104.9 +/- 9.7 pM. This concentration is in the range which has been shown to stimulate ACTH and beta-endorphin secretion in vitro. These data support the hypothesis that a molecule with the same or similar structure as synthetic ovine CRF is a physiologically significant hypothalamic releasing factor.