Fe(3+)-NTA投与糖尿病ラットのβ細胞開口分泌の電顕的観察

内分泌腺細胞の分泌時間は瞬時とされていることから,一般的にその分泌像の形態的観察には,分泌を促進せしめる実験系が用いられている.又膵ラ氏島B細胞分泌の超微形態は,専ら浸漬固定標本で観察されている.今回,我々は分泌が遅延している動物で,高速還流した膵ラ氏島細胞について観察した.即ち,前報と同様のFe(3+)-NTA誘発糖尿病ラットの上行大動脈より2%グルタールアルデヒド150mlを15ml/minの速度で還流固定し,ラ氏島B細胞のβ顆粒分泌像に焦点を絞って観察した.その結果,前報の浸漬固定法では観察されなかった開口分泌像が多数観察され得た.対照の健常動物に比べ, Fe(3+)-NTA投与動物では,分泌直前から分泌後に至るいろいろな段階のβ顆粒の分泌過程が観察された.以上の結果から,開口分泌像の電顕的観察にはむしろ本実験系のように細胞分泌を障害ないし低下せしめ,高速還流固定法を用いることが必要であると結論した.

The secretion time of endocrine cells is known to be momentary. Therefore, morphologic proof of the secretory mode have relied heavily on various animal models which were treated to accelerate secretion. Ultrastructure, concerning B-cell secretion from Langhans' islets of the pancreas, has been based on immersion-fixation specimens. As an experimental model of prolonged endocrine secretion, we used rat pancreas tissues which were rapidly perfused with a fixative. The fixation process, as reported previously, was 150 ml of 2% glutaraldehyde flushed at 15 ml per minute through the ascending aorta of Fe(3+)-NTA-treated diabetic rats. Afterwards, an ultrastructural study focused on the secreting mode of beta-granules in B-cell of Langhans' islets. This procedure proved an “open secretion” of beta-granules from B-cells; this phenomenon has never been observed in the previous immersion-fixation specimens. Contrary to non-treated normal rats, the varied stages of beta-granule secretion, including immediately before as well as after the secretion, were demonstrated in Fe(3+)-NTA-treated rats. We wish to emphasize the use of rapid perfusion-fixation technique in animal models with a delayed rather than accelerated state of endocrine secretion in order to investigate ultrastractural aspects of “open secretion”.