中华鲟(Acipenser sinensis)脑垂体的形态和ACTH细胞定位

THE ACIPENSER SINENSIS PITUITARY:MORPHOLOGY AND ACTH CELL LOCATION

为研究中华鲟(Acipenser sinensis)神经内分泌系统的基本结构和功能,本文对中华鲟脑垂体的组织形态进行了观察,结果表明中华鲟的神经垂体较小,腺垂体可分为前、中和后腺垂体三部分,神经垂体形成分支插入后腺垂体。中华鲟垂体还有一个特点是有分支的垂体裂。前腺垂体位于垂体前侧,细胞间隙大,细胞分散呈窦状。中腺垂体细胞间隙小,细胞密集呈条索状,嗜酸性细胞和嗜碱性细胞区分明显。后腺垂体包围在神经垂体周围。腺垂体中有长且分支的垂体裂,腺垂体形成许多突起深入其中,垂体裂周围的细胞密集,染色深,排列成类似上皮组织的形态。免疫组化结果表明,中华鲟脑垂体ACTH细胞主要分布于后腺垂体。ACTH的前体基因是POMC,RT-PCR证明其主要分布在脑垂体中,在体内其他组织中基本检测不到。编码ATCH的片段位于POMC中最保守的区域。预测发现POMC基因有一个26氨基酸的信号肽,将不带信号肽的POMC基因插入表达载体。再转染HELA细胞POMC主要在细胞质中表达,而带有信号肽的POMC蛋白在细胞内很少,推测可能分泌到胞外,信号肽对POMC表达和功能发挥起重要作用,本研究结果可为该基因在中华鲟神经内分泌研究中提供参考。

To understand the structure and function of the neuroendocrine system of Chinese sturgeon Acipenser sinensis, we studied the morphology of the pituitary and the adrenocorticotropin （ACTH） ceils in the pituitary gland. The fish were sampled from Changjiang （Yangtze） River estuary, body weight -100g. We observed that the fish has a small neurohypophysis （Ne）, and adenohypophysis could be divided into three parts： proadenophypophysis （Pa）, mesoadenohypophysis （Ma） and metaadenohypophysis （Me）. Pa is located in the front of the pituitary. The Ne is small and finger-like in the middle part, not in the Pa as most teleost fish. Another feature is the presence of a large hypophysial cleft （HC） with numerous digitations. The cells of adenohypophysis contained the basophil cells, acidophil ceils, and chromophobe cells, and they were different in shape and in distribution. The cells around the HC looked like epithelial lined. Immunohistochemical study showed that the ACTH cells in the pituitary gland distributed mainly in the Me. The precursor gene of ACTH is POMC （pro-opiomelanocortin）, and RT-PCR shows that it distributed in the pituitary but other tissues. The ATCH-encoding region was located in the most conservative region of the POMC. It is predicted that the POMC gene has a 26-amino-acid signal peptide. The POMC gene with or without signal peptide was cloned into the expression vector. After transfection into HeLa cells, POMC without signal peptide was expressed in the cytoplasm, while the POMC protein with signal peptide was very little in the cytoplasm. Proteins with a signal peptide are rare in cells and they probably secreted out of the cells. Therefore, signal peptide plays an important role in the expression and function of POMC. The findings shall provide a reference for the study of Chinese sturgeon neuroendocrine.