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  • Author: S C Sharma x
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Role of oestradiol-17β in the regulation of synthesis and secretion of human chorionic gonadotrophin by first trimester human placenta

S C Sharma, P Purohit, and A J Rao

ABSTRACT

Inhibition of aromatase, a key enzyme in the biosynthesis of oestradiol-17β, by the addition of 1,4,6-androstatrien-3,17-dione resulted in a significant increase in the levels of immunoreactive human chorionic gonadotrophin (hCG) in the medium and tissue. This increase was partially reversed by the simultaneous addition of oestradiol-17β. These effects on the levels of immunoreactive hCG were also reflected by the increased levels of mRNA specific for the α and β subunits of hCG following the addition of the aromatase inhibitor. However, addition of tamoxifen resulted in a drastic decrease in the levels of both the messages. Based on these results, it is suggested that the synthesis of hCG is negatively modulated by oestradiol-17β in the human placenta.

DOI:
https://doi.org/10.1677/jme.0.0110091
Volume 11: Issue 1,
Pages:
91–101 (11 total)
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Characterization of rat gastric inhibitory peptide cDNA

S. K. Sharma, C. Austin, A. Howard, G. Lo, C. G. Nicholl, and S. Legon

ABSTRACT

Gastric inhibitory peptide (GIP) is a 42 amino acid gastrointestinal peptide which inhibits gastric acid secretion and stimulates pancreatic insulin secretion in the presence of glucose. Here we report the sequence of the cDNA encoding the rat GIP precursor. PreproGIP was 144 amino acids in length and comprised the GIP peptide itself, N- and C-terminal flanking peptides of 22 and 59 amino acids respectively and a typical hydrophobic signal peptide. The sequence indicated that GIP is released from its precursor by cleavage at single arginine residues. The C-terminal flanking peptide may have an important function since it was well conserved and contained a region of 16 amino acids with only a single, conservative replacement. Rat GIP mRNA was found in the duodenum and jejunum. Levels of GIP mRNA in the duodenum were increased twofold after a period of 2 days of starvation. There was no detectable expression of the GIP gene in other parts of the gastrointestinal tract or in other endocrine tissues. However, in pancreatic mRNA preparations, a larger mRNA was detected after low stringency hybridization. This could represent a further member of this gene family.

DOI:
https://doi.org/10.1677/jme.0.0090265
Volume 9: Issue 3,
Pages:
265–272 (8 total)