科研之友
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摘要
Recent evidence has shown that d-aspartate modulates hormone secretion in the vertebral neuroendocrine system. Because only d-aspartate oxidase (DDO) can degrade d-aspartate, we determined DDO localisation in the pituitary and pineal glands to elucidate the control mechanisms of local d-aspartate concentration. Brain tissues and pituitary and pineal glands of the female pigs contained a similar DDO activity of 0.38-0.66 U/g protein. However, approximately ten-fold higher concentrations of d-aspartate (0.27-0.35 mu mol/g protein) were found in both glands. To determine the distribution of immunoreactive DDO, we made a rabbit polyclonal antibody specific to porcine DDO using a recombinant porcine enzyme. DDO immunoreactivity was found in the cytoplasm of a subgroup of cells in the anterior and intermediate lobes, in a part of nerve processes and terminals in the posterior lobe, and in the cytoplasm of a small group of pinealocytes. We used dual-label immunocytochemistry to determine which pituitary hormones colocalise with DDO, and whether DDO and d-aspartate immunoreactivity is reciprocal. In the pituitary gland, almost all proopiomelanocortin-positive cells colocalised DDO, whereas only growth hormone-positive cells colocalised d-aspartate. d-Aspartate immunoreactivity was not detected where DDO immunoreactivity was found. The present study suggests that DDO plays important roles to prevent undesirable off-target action of d-aspartate by strictly controlling local d-aspartate concentration in the pituitary and pineal glands.
- 出版日期2010-11
