Santillo A, Monteforte R, Raucci F, D'Aniello A, Baccari G Chieffi
Dipartimento di Scienze della Vita, Seconda Università di Napoli, Caserta, Italy.
J Exp Zool A Comp Exp Biol. 2006 Aug 1;305(8):610-9. doi: 10.1002/jez.a.301.
High concentrations of free D-aspartate (D-Asp), an amino acid well known for its neuroexcitatory activity, are endogeneously present in the Harderian gland (HG) of the lizard Podarcis s. sicula. This orbital gland consists of two different parts: the medial part, which is prevalently a mucous acinar gland, and the lateral part, which is a serous tubulo-acinar gland. To determine the physiological effect of D-Asp on exocrine secretion in HG, D-Asp (2.0 micromol/g b.w.) was injected intraperitoneally into lizards. We found that highest accumulations of exogenous D-Asp in HGs occurred 15 hr after the injection. Specifically, exogenous D-Asp prevalently stimulated serous secretion from the lateral portion of the gland, where immunohistochemical analysis revealed a major accumulation. Similarly, in the medial part of the gland, highly sulfated mucosubstances were observed after D-Asp injection. Further, in both parts of the HG, the electron microscope revealed euchromatic nuclei, a prominent rough endoplasmic reticulum, as well as numerous secretory granules within the acinar cells. Thus, following D-Asp injection, a 60% increase in HG total protein was detected. In addition, exogenous D-Asp induced changes in the electrophoretic pattern of HG. In conclusion, although further investigations are still needed to clarify the molecular pathway induced by D-Asp in exocrine secretion, this study does indicate that free D-Asp plays a significant role in the secretory activity of this gland.
高浓度的游离D-天冬氨酸（D-Asp）是一种以神经兴奋活性而闻名的氨基酸，内源性地存在于意大利壁蜥（Podarcis s. sicula）的哈德氏腺（HG）中。这个眶腺由两个不同的部分组成：内侧部分，主要是黏液性腺泡腺；外侧部分，是浆液性管泡状腺。为了确定D-Asp对哈德氏腺外分泌的生理作用，将D-Asp（2.0微摩尔/克体重）腹腔注射到蜥蜴体内。我们发现，注射后15小时，哈德氏腺中外源性D-Asp的积累量最高。具体而言，外源性D-Asp主要刺激腺体外侧部分的浆液分泌，免疫组织化学分析显示该部位有大量积累。同样，在腺体的内侧部分，注射D-Asp后观察到高度硫酸化的黏液物质。此外，在哈德氏腺的两个部分，电子显微镜均显示腺泡细胞内有常染色质核、突出的粗面内质网以及大量分泌颗粒。因此，注射D-Asp后，检测到哈德氏腺总蛋白增加了60%。此外，外源性D-Asp诱导了哈德氏腺电泳图谱的变化。总之，尽管仍需要进一步研究来阐明D-Asp在外分泌中诱导的分子途径，但这项研究确实表明游离D-Asp在该腺体的分泌活动中起重要作用。
