Bestetti G E, Brändli P, Rossi G L
Division of Experimental Pathology, University of Berne, Switzerland.
Acta Anat (Basel). 1994;149(3):215-20. doi: 10.1159/000147579.
Pituitary cells transport secretory products from deep cytoplasmic portions towards the subplasmalemmal region (SPL) by two mechanisms: (a) the regulated, secretagogue-dependent and (b) the secretagogue-independent constitutive pathway. Since thyrotropin (TSH) secretion is impaired in diabetes, we studied both pathways in the thyrotropes of control and streptozocin (STZ)-treated male rats. By electron microscopy, we measured the nucleus and cytoplasm area and counted the secretory granules. In 4 selected SPL (500 nm deep) areas per cell we also counted the marginated secretory granules and measured their area. Moreover, after TSH indirect immunogold labelling we counted immunogold particles on (a) the secretory granules of the SPL and (b) the intergranular SPL cytoplasm. To check the background staining we also counted immunogold particles on nonthyrotropic cells. In diabetic compared with control thyrotropes we found: (a) cytoplasmic atrophy and increased number of secretory granules per cytoplasm unit area, (b) reduced number of secretory granules in the SPL (blunted regulated secretion), (c) larger secretory granules in the SPL (abnormal secretory granule maturation), (d) decreased immunogold labelling of secretory granules in the SPL (reduced TSH transported by each secretory granule towards the cell membrane) and (e) decreased immunogold labelling of the intergranular SPL cytoplasm (blunted constitutive secretion). Our data suggest reduced regulated and constitutive TSH secretion and may thus contribute to a better understanding of the hypothyroidism in STZ-diabetic rats.
垂体细胞通过两种机制将分泌产物从细胞质深部转运至亚膜下区域（SPL）：（a）受调节的、促分泌素依赖途径和（b）促分泌素非依赖的组成型途径。由于糖尿病患者促甲状腺激素（TSH）分泌受损，我们研究了对照和链脲佐菌素（STZ）处理的雄性大鼠促甲状腺细胞中的这两种途径。通过电子显微镜，我们测量了细胞核和细胞质面积，并对分泌颗粒进行计数。在每个细胞中4个选定的SPL区域（深500nm），我们还对边缘分布的分泌颗粒进行计数并测量其面积。此外，在TSH间接免疫金标记后，我们对（a）SPL的分泌颗粒和（b）颗粒间SPL细胞质上的免疫金颗粒进行计数。为检查背景染色，我们还对非促甲状腺细胞上的免疫金颗粒进行计数。与对照促甲状腺细胞相比，在糖尿病促甲状腺细胞中我们发现：（a）细胞质萎缩且每个细胞质单位面积的分泌颗粒数量增加，（b）SPL中分泌颗粒数量减少（调节性分泌减弱），（c）SPL中分泌颗粒更大（分泌颗粒成熟异常），（d）SPL中分泌颗粒的免疫金标记减少（每个分泌颗粒向细胞膜转运的TSH减少），以及（e）颗粒间SPL细胞质的免疫金标记减少（组成型分泌减弱）。我们的数据表明TSH的调节性分泌和组成型分泌减少，因此可能有助于更好地理解STZ糖尿病大鼠的甲状腺功能减退。
