Localization, Transport, and Uptake of [formula omitted]-Aspartate in the Rat Adrenal and Pituitary Glands

• Published in: Archives of biochemistry and biophysics 2001-01, Vol.385 (2), p.242-249
• Main Authors: Lee, Jen-Ai, Long, Zhiqun, Nimura, Noriyuki, Iwatsubo, Takeshi, Imai, Kazuhiro, Homma, Hiroshi
• Format: Article
• Language: English
• Subjects: [formula omitted]-amino acids; [formula omitted]-aspartate; adrenal gland; glutamate transporter; immunohistochemistry; pituitary gland
• ISSN: 0003-9861; 1096-0384
• DOI: 10.1006/abbi.2000.2163

Large amounts of d-aspartate (d-Asp) are present in the rat adrenal and pituitary glands. d-Asp is thought to be synthesized in the mammalian body and also accumulates in various tissues following intraperitoneal or intravenous administration. This report examines the origins of d-Asp in the adrenal and pituitary glands. We administered d-Asp to male rats intraperitoneally and immunolocalized this exogenous d-Asp in adrenal and pituitary tissue, using an anti-d-Asp antiserum which was previously developed in our laboratory. d-Asp levels in the rat adrenal gland have been shown to undergo a transient increase at 3 weeks of age and to decrease rapidly thereafter. We found that in the adrenal gland, exogenous d-Asp administered intraperitoneally was incorporated into the same region of the adrenal cortex in which endogenous d-Asp was present. By Northern and Western blot analysis and immunohistochemistry of glutamate (Glu) transporter, we also found that expression of the Glu transporter (GLAST), which has an affinity for d-Asp, transiently increased at 3 weeks of age and that localization patterns of the Glu transporter within the tissue were almost coincident with those of endogenous d-Asp. These observations suggest that d-Asp in the adrenal cortex of 3-week-old male rats is primarily acquired by uptake from the vascular system. We have previously shown that d-Asp is specifically localized in prolactin (PRL)-containing cells in the anterior lobe of the adult rat pituitary gland. Here we report that in the pituitary gland, exogenous d-Asp accumulated in endothelial cells, but not in PRL-containing cells. Northern and Western blot analysis and immunohistochemistry of Glu transporter revealed that developmental changes in the Glu transporter (GLAST) expression did not correlate with tissue levels of d-Asp and that the Glu transporter was not expressed in PRL-containing cells. These observations suggest that, in contrast to the adrenal gland, most of the d-Asp in the pituitary gland of adult male rats originates inside the gland itself.