α-Melanocyte-stimulating-hormone precursors in the pig pituitary

The occurrence of intermediates from the processing of ACTH-(1-39) [adrenocorticotropic hormone-(1-39)] to alpha-melanocyte-stimulating hormone was investigated in normal pig pituitaries by the use of sensitive and specific radioimmunoassays for ACTH-(1-13), ACTH-(1-14), ACTH-(1-13)-NH2 and ACTH-(1-39). Fractionation by reverse-phase h.p.l.c. revealed ACTH(1-17) and their acetylated analogues. The intermediate lobe contained NO-diacetyl-ACTH-(1-13)-NH2, N-acetyl-ACTH-(1-13)-NH2 and ACTH-(1-13)-NH2. In addition, the corresponding ACTH-(1-14) peptides (the glycine-extended precursor of the amidated peptides) were detected in lower amounts in both the intermediate lobe and the anterior lobe. ACTH-(1-17), ACTH-(1-13) and their acetylated analogues could not be detected in the anterior lobe or the intermediate lobe. The results suggest that an endopeptidase initially cleaves ACTH-(1-39) at the Lys-16-Arg-17 bond. ACTH-(1-16) is then processed by a pituitary carboxypeptidase to ACTH-(1-14) and ACTH-(17-39) by the aminopeptidase to ACTH-(18-39).

High content of tyrosine and arginine in peptides and proteins from the growth hormone producing cells of the adenohypophysis.

Fluorescence histochemistry has demonstrated an abundance of tyrosine and arginine residues in the growth hormone (GH) producing cells of the pituitary of several mammals. Granules from pig pituitaries were purified by passage through a succession of Millipore filters followed by centrifugation on a continuous sucrose gradient. One granular fraction, rich in GH, was found to contain proteins or peptides rich in tyrosine and arginine. Gel chromatography of the acid-soluble components from sedimented pituitary granules revealed that the arginine- and tyrosine-rich material was heterogeneous. The arginine-containing peptides and proteins could be separated into several peaks with molecular weights from 5000-10,000 and higher. The tyrosine-containing material comprised one peptide with a molecular weight of 5000-10,000 and another much smaller peptide. Since GH itself is not excessively rich in either tyrosine or arginine, the tyrosine- and arginine-containing proteins or peptides probably constitute as yet unidentified granular components, distinct from GH itself.

Peptides with NH2-terminal tryptophan in adrenocorticotrophic hormone and melanocyte-stimulating hormone granules of adenohypophysis.

Fluorescence microscopy has demonstrated formaldehyde-ozone-induced fluorescence in the pars intermedia cells (melanocyte-stimulating hormone cells) and in certain cells of the pars distalis of the mammalian pituitary. From histochemical and chemical evidence the fluorescence is believed to reflect the presence of peptides with NH2-terminal tryptophan. In the pars distalis of hamster, cat and pig pituitary, the cells that exhibit formaldehyde-ozone-induced fluorescence have now been identified as adrenocorticotrophic hormone (ACTH) cells by immunohistochemistry. Granules from pig pituitaries were purified by passage through a succession of Millipore filters followed by centrifugation on a continuous sucrose gradient. Two granular fractions were identified by electron microscopy and found to contain high concentrations of peptides with NH2-terminal tryptophan as well as high ACTH bioactivity. These fractions, when pelleted and analyzed histochemically, displayed formaldehyde-ozone-induced fluorescence and ACTH-like immunoreactivity.

Selective neutralization of the luteinizing activity of gonadotrophic extracts of pituitary by anti-sera

Gonadotrophic extracts from different sources vary greatly in their relative capacity to cause follicular stimulation, ovulation and luteinization in the ovaries of the immature rat. Thus the effectiveness of crude extracts of anterior pituitary depends largely on the species of animal from which the pituitaries are obtained (Hill 1934). Extracts of horse pituitary cause great activity in the immature ovaries, leading to the production of abundant large follicles and corpora lutea with or without ovulation. Extracts of sheep and pig pituitaries are much less effective, while extracts of ox pituitary show little activity when tested on the immature rat. Extracts from urine of pregnancy cause some growth of the follicles, which tend to become heavily luteinized, but those of urine from women after the menopause and from ovariectomized women show greater folliclestimulating properties (Zondek 1930).