Corticotropic Peptides in the Human Fetal Pituitary*

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Abstract
Peptides were extracted from 11 human fetal pituitaries (11–19 weeks of gestation) and separated by reversedphase high pressure liquid chromatography. No correlation between gestational age and the pituitary content of immunoreactive (IR)-ACTH and IR-αMSH could be established. IR-β-Endorphin levels increased with the gestational age of the fetus. The bioactivity of the high pressure liquid chromatography fractions of pituitaries from 5 fetuses of 15–19 weeks of gestation was tested by addition to autologous fetal adrenal cells in monolayer culture. The production of dehydroisoandrosterone sulfate (DHAS) and cortisol (F) by the cells was determined by RIA. Three corticotropic factors were detected that stimulated steroid production by the adrenal cells. The major IR-ACTH peak, which eluted with the same retention time as standard human ACTH-(1–39), stimulated DHAS and F production by adrenal cells from 15- to 19-week-old fetuses. The minor IR-ACTH peak eluted with the retention time expected for human ACTH-(1–38) and stimulated DHAS in all of the fetal adrenals tested (15–19 weeks of gestation) but stimulated F in only the adrenal cells from older fetuses (18 and 19 weeks). The third corticotropic factor had no associated ACTH, αMSH, or β-endorphin immunoreactivity and eluted with a retention time shorter than that of these 3 standard peptides. The material contained in these fractions stimulated DHAS and F production by adrenal cells from older fetuses (18 and 19 weeks), but only DHAS production by cells from younger fetuses (15–17 weeks). The identity of this third corticotropic factor has not yet been established. Only one major peak of IR-αMSH was detected that eluted with the same retention time as isolated bovine desacetyl-αMSH. No corticotropin-like intermediate lobe peptide was detected in any of the pituitary extracts.

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