Effects of early embryonic bursectomy and opotherapic substitution on the functional development of the adrenocorticotropic axis

Functional development of the adrenocorticotropic axis was inferred from plasma ACTH and corticosterone levels in intact and embryonically bursectomized (BFX) embryos and chicks from 8 days before to 56 days after hatch. Bursectomy was surgically made at 80 h of incubation and resulted in various alterations in developing adrenocorticotropic axis: ether stress-induced hormonal stimulation could be detected more precociously in BFX (day-6) than in intact embryos; the non stress-responsive period of newly hatched controls did not appear in BFX chicks; BFX young adult chicken exhibited quite smaller responses to stress than controls. In ovo injection of bursin (Lys-His-Gly-NH2) to 6- and 9-days old BFX embryos could restore normal adrenocorticotropic development provided convenient doses of tripeptide were used: administration of 100 fg or 100 pg of bursin was effective to restore normal hormonal levels at all stages studied whereas 100 micrograms was effective at embryonic stages only. The tripeptide Lys-His-Gly-NH2 is suggested as a possible signal from the immune B system directed at the hypothalamo-hypophysial-adrenocortical axis.