| Budget Amount *help |
¥1,800,000 (Direct Cost: ¥1,800,000)
Fiscal Year 1988: ¥600,000 (Direct Cost: ¥600,000)
Fiscal Year 1987: ¥1,200,000 (Direct Cost: ¥1,200,000)
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| Research Abstract |
Neuromedin B, originally isolated from porcine spinal cord, is a decapeptide which shows remarkable sequence homology with members of the family of bombesin-like peptides, particularly litorin and ranatensin. The peptide potently stimulates the contraction of guinea pig uterus and the secretion of insulin, enteroglucagon, gastrin and cholecystokinin in rat. In the rat and guinea-pig, it is distributed not only in the gastrointestinal tract and pancreas but also in the brain, concentrating especially in the pituitary.
Recently, Steel et al. demonstrated that neuromedin B was present mainly in the thyrotropic cells of the anterior pituitary of rat and mouse, and that the content in the pituitary changed according to thyroid function. However, the physiological role of neuromedin B in the regulation of TSH secretion in the pituitary is not clear yet. In order to clarify the effect of neuromedin B on TSH secretion, we performed an in vitro study using a perifusion system to measure the release of TSH from rat pituitary preparations.
In this system, the increment in TSH release under continuous TRH (1 ng/ml) stimulation for 60 min was 8.10 0.64 ng/mg pituitary (mean SE). TRH-stimulated incremental amounts of TSH release were markedly reduced in a dose-dependent manner by the addition Neuromedin B; in the presence of 10 and 10^<-5> M neuromedin B, they were 4.65 0.83 and 3.79 0.48 ng/mg pituitary, respectively. Furthermore, we studied the effect of neuromedin B on the basal release of TSH from perifused rat pituitaries. At concentrations of both 10^<-7> and 10^<-5> M, neuromedin B significantly inhibited the basal release of TSH.
These results suggest that neuromedin B may be one of the factors which regulate the secretion of TSH in the pituitary gland.
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