Synthesis, purification and biological evaluation of porcine corticotropin-releasing factor

The 41-residue sequences of recently identified porcine corticotropin-releasing factors [I1e⁴⁰]pCRF and [Asn⁴⁰]pCRF were assembled on a benzhydrylamine resin support. Deprotection and cleavage from the resin were accomplished by HF treatment. The crude peptides were purified by HPLC. The homogeneity of the final materials, obtained in 0.2% and 0.4% overall yield for [I1e⁴⁰]pCRF and [Asn⁴⁰]pCRF respectively, was assessed after the isolation by HPLC and amino acid analysis. Both sequences of the synthetic 41-residue pCRF stimulated the release of corticotropin (ACTH) from superfused rat pituitary cells on a column, the responses being related to a log-dose of CRF in the range of 1-20 ng/ml. [I1e⁴⁰]pCRF and [Asn⁴⁰]pCRF also augmented the in vivo release of ACTH in rats pretreated with chlorpromazine, morphine and Nembutal. [I1e⁴⁰]pCRF appeared to be equipotent to ovine CRF and about twice as active as [Asn⁴⁰]pCRF. The data indicate that synthetic porcine [I1e⁴⁰]pCRF and [Asn⁴⁰]pCRF have high biological activity.