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A PTH/PTHrP receptor antagonist blocks the hypercalcemic response to estradiol-17b
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Resumo(s)
Estradiol (E2) increases circulating
calcium and phosphate levels in fish, thus acting as a hypercalcemic
and hyperphosphatemic factor during periods of high calcium
requirements, such as during vitellogenesis. Since parathyroid hormone
(PTH)-related protein (PTHrP) has been shown to be calciotropic
in fish, we hypothesized that the two hormones could be mediating
the same process. Sea bream (Sparus auratus) juveniles receiving a
single intraperitoneal injection of piscine PTHrP(1-34) showed an
elevation in calcium plasma levels within 24 h. In contrast, injections
of the PTH/PTHrP receptor antagonist PTHrP(7-34) decreased circulating
levels of calcium in the same period. Intraperitoneal implants of
estradiol-17 (E2; 10 g/g) evoked significant increases of circulating
plasma levels of calcium and phosphorus and a sustained increases of
circulating plasma levels of PTHrP. However, a combined treatment
of E2 and PTHrP(7-34) evoked a markedly lower calcium response
compared with E2 alone. We conclude that PTHrP or a related peptide
that binds the PTH/PTHrP receptor mediates, at least in part, the
hypercalcemic effect of E2 in calcium and phosphate balance in fish.
Descrição
Palavras-chave
Fish Calcium Phosphate
Contexto Educativo
Citação
Editora
American Physiological Society