Inhibition of Releasing-Hormone-lnduced Secretion of TSH and LH by Calcitonin

Leicht, E.; Bíró, G.; Weinges, K. F.

doi:10.1055/s-0028-1093816

Cited by 65 publications

(19 citation statements)

References 2 publications

(2 reference statements)

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“…tropes is in good agreement with the hypothesis that CT stimulates LH, GH and TSH release at the hypothalamic level (Cantálamessa et al 1978;Leicht et al 1974;Minamitani et al 1985).…”

Section: Discussionsupporting

confidence: 89%

Evidence for direct action of calcitonin in the rat pituitary gland

Morel

Chabot²,

Enjalbert³

et al. 1989

Acta Endocrinologica

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Classic concepts of calcitonin (CT) function have focused on the effects of CT on calcium homeostasis. More recently CT actions on brain and pituitary have been investigated. In order to evaluate the effects of CT on the anterior pituitary gland we studied the action(s) of CT in vitro and visualized endogenous CT in adult male rat pituitary gland by immunocytochemistry on ultrathin sections obtained by cryoultramicomy. In vitro study using dispersed anterior pituitary cells indicated that CT stimulated the secretion of PRL, whereas the secretion of GH, TSH and LH was not affected. CT\ x=req-\ like immunoreactivity was observed in lactotropes only. The other pituitary cell types were not immunoreactive.In lactotropes, immunostaining was observed in the cytoplasm and in the nucleus. In the cytoplasm, CT-like immunoreactivity was visuzalized in the cytoplasmic matrix and in the secretory granules. In the nucleus, immunostaining was distributed primarly in the euchromatin, in the vincinity of heterochromatin region. CT-like immunoreactivity was also observed at the plasma membrane but was only scarce. No reaction product was found when anti-CT serum pre-incubated with CT was used. In conclusion, these results bring evidence for a direct action of CT on lactotrope regulation in vitro as well as in intact animals. Calcitonin (CT), a 32 amino acid peptide with a 1,7-disulfide bridge and a proline amide at the carboxyl terminus, is synthesized by the C cells of the mammalian thyroid (Bussolati & Pearse 1967; Copp et al. 1962). Classic concepts of CT function have focused on the effects of CT on calcium homeostatis (Munson 1976). However, recent studies have indicated a broader range of CT action (Cantalamessa et al. 1978; Leicht et al. 1974) namely on the central nervous system (Freed et al. 1979; Morley et al. 1981). In addition, it has also been shown that CT can exert stimulatory or inhibitory action on the secretion of many adenohypophyseal hor¬ mones in basal conditions or in response to appro¬ priate stimuli (Cantalamessa et al. 1978; Pecile et al. 1981). Moreover, the presence of specific and saturable binding sites for CT have been recently demonstrated in the rat pituitary glands (Goltzman & Mitchell 1985; Maurer et al. 1983; Rizzo & Goltzman 1981). These different observa¬ tions suggest a possible involvement of CT in pitui¬ tary secretory activity. The aims of the present study were to investigate the in vitro effect(s) of CT on the release of adeno¬ hypophyseal hormone(s) and to demonstrate en¬ dogenous CT in anterior pituitary cell(s) at the subcellular level. Materials and Methods In vitro study Cell culture. Cell dispersion was performed according to Hospins 8c Farquhar (1973). Anterior pituitaries from Wistar female rats (Charle Rivers, France) were dissectedinto small pieces (about 0.5 mm in diameter) and incu¬ bated for 15 min with 0.5% trypsin in Dulbecco Minimum Essential Medium (DMEM) at 37°C. DNase (2 mg/1) was then added for 1 min to the medium. After enzymatic di¬ gestion the medium was removed an...

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“…tropes is in good agreement with the hypothesis that CT stimulates LH, GH and TSH release at the hypothalamic level (Cantálamessa et al 1978;Leicht et al 1974;Minamitani et al 1985).…”

Section: Discussionsupporting

confidence: 89%

Evidence for direct action of calcitonin in the rat pituitary gland

Morel

Chabot²,

Enjalbert³

et al. 1989

Acta Endocrinologica

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“…Besides the hypocalcemic effect of CT, it is well established that CT administration shows regulatory effects on a variety of hormone secretion. Secretion of gastrin [6], insulin [3], GH [16], TSH [15], prolactin [20], and prostaglandin [4] were suppressed by the preinfusion of CT. On the other hand, hormone secretions were stimulated by CT infusion in the following hormones, such as ACTH [14], somatostatin [5,10,17], and beta-endorphin [14] secretions. Auto-regulation of CT secretion has been suggested as a feedback mechanism by some researchers using porcine thyroid slices [1,21].…”

Section: Introductionmentioning

confidence: 96%

Exogenous Calcitonin Suppresses Growth Fraction of Thyroid C Cells

Mori

Nakamura

Iteya

et al. 2003

Acta Histochem. Cytochem

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Calcitonin (CT) is a peptide hormone synthesized and secreted by the parafollicular (C) cells of the thyroid. Little is known about the mechanisms controlling proliferation of C cells by other humoral factors including CT, and there is no report that CT suppresses C cell proliferation. The effects of short-term administration of CT on C cell growth fraction were analyzed using BrdU and CT double immunohistochemical method in the rat thyroid. Continuous administration of 0.4 IU/kg and 40 IU/kg synthetic salmon CT for 14 days induced dosedependent suppression of BrdU labeling number of C cells without decrease of C cell to the total thyroid follicular cell ratio. These results suggest that exogenous CT may induce negative feedback to C cell proliferation in the thyroid.

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“…Effects of sCT on increased plasma E 2 levels might be due to its action either on high pituitary GtH release or its direct action on ovarian follicles. Intravenous infusion of CT in human caused a calciumindependent reduction in thyrotropin and LH secretion in response to hypothalamic releasing hormone (Leicht et al, 1974). Inhibition of sCT on secretion of progesterone and GnRH-stimulated pituitary LH has also been reported (Tan et al, 1994).…”

Section: Discussionmentioning

confidence: 91%