RESUMO
RT-PCR was undertaken on total RNA extracts from bone and scales of the rainbow trout, Oncorhynchus mykiss. The rainbow trout estrogen receptor (ER)-specific primers used amplified a single product of expected size from each tissue which, using Southern blotting, strongly hybridized with a 32P-labelled rtER probe under stringent conditions. These data provide the first in vivo evidence of ER mRNA in bone and scale tissues of rainbow trout and suggest that the effects of estrogen observed in this study (increased bone mineral and decreased scale mineral contents, respectively) may be mediated directly through ER.
Assuntos
Osso e Ossos/metabolismo , Cálcio/metabolismo , Estradiol/farmacologia , Oncorhynchus mykiss/metabolismo , Receptores de Estrogênio/biossíntese , Animais , Northern Blotting , Osso e Ossos/efeitos dos fármacos , Fosfatos/metabolismo , Reação em Cadeia da Polimerase , RNA Mensageiro , Receptores de Estrogênio/genéticaRESUMO
During reproduction, female teleost fish display increased plasma estrogen and greatly increased total plasma calcium concentrations; the main source of this calcium seems to be the scale. Osteonectin, a collagen-binding glycoprotein, is a major noncollagenous constituent of mammalian bone and is a product mainly of the osteoblasts. RT-PCT has been applied to clone and sequence part of the osteonectin gene from the goldfish, Carassius auratus. The use of a goldfish scale cell line (GFS) and a specific probe to goldfish osteonectin mRNA has allowed the study of the potential effects of estrogen and other calcitropic hormones on the cells derived from the scales. Osteonectin mRNA was detected in teleost bone, scale, and GFS cells by Northern blot analysis, hybridising to a transcript of approximately 1.6 kb. Expression of osteonectin mRNA was markedly down-regulated by 17beta-estradiol (10(-8) to 10(-11) M) in a dose-dependent fashion but was unaffected by calcitriol, TGFbeta, IL-1beta, calcitonin, and PTHrP. Down-regulation of osteonectin by estrogen is further evidence that estrogen participates in calcium homeostasis during vitellogenesis, acting directly on the cells responsible for matrix and mineral fluxes in scales.