Electrochemistry on Mars.
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Biomedical subjects
Publications and source records attributed to R Geis.
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We examined to which extent adrenocorticotropin (ACTH)-like substances are cleavable into alpha-melanotropin (MSH)-like material by application of exogenous enzymes on pituitary sections prior to immunocytochemical stainings. In pro-opiomelanocortin (POMC) cells of the anterior lobe from developing rats (1 to 21 postnatal days) at least one of two cells contained alpha-MSH-like immunoreactivity besides ACTH-like immunostaining. Pretreatment of these tissue sections with tryptic enzymes enhanced remarkably alpha-MSH-like immunostaining. In contrast, alpha-MSH-like immunoreactivity was almost not detectable in anterior lobes from adult rats, also after treatment with enzymes. After adrenalectomy (ax) POMC cells in anterior lobes behaved similarly: a few days after the operation almost all ACTH cells contained also alpha-MSH immunostaining, whereas after more than two weeks alpha-MSH immunostaining was nearly absent, also after application of enzymes. In contrast to rats, in young and adult guinea pig pituitaries all ACTH-like immunoreactivity was prevented by treatment with tryptic enzymes. These observations are consistent with the assumption that occurrence of ACTH- and alpha-MSH-like substances in rat pituitaries is regulated by a protection mechanism against proteolytic cleavage in the ACTH sequence which appears with delay in differentiating and maturing cells.
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The levels of immunoreactive leucine-enkephalin, alpha-neo-endorphin, dynorphin (1-17) and dynorphin (1-8) have been determined in the hypothalamus and posterior pituitary from male and female Brattleboro rats homozygous (unable to produce vasopressin) and heterozygous (producing vasopressin) for diabetes insipidus, and from male and female Long Evans rats. In the hypothalamus we found no significant differences in the levels of these peptides while there were great differences in extracts from the posterior pituitary: female homozygous animals have greatly reduced levels in all four peptides compared to the heterozygous controls. In male homozygous animals the differences in the dynorphin (1-17) and leucine-enkephalin levels were small whereas the concentrations of alpha-neo-endorphin and dynorphin (1-8) showed a significant decrease compared to the male heterozygous controls. The results indicate a reduction in opioid peptides linked to the vasopressin deficiency in a partially sex dependent manner.