Identification ultrastructurale et étude immunocytochimique des cellules à somatostatine de la muqueuse antrale du lapin et de la souris

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Abstract
Les techniques d'immunofluorescence, d'immunoenzymatique, d'imprégnation ou de coloration sélective des cellules endocrines digestives, et de microscopie électronique ont été combinées pour permettre l'identification et l'étude des cellules à somatostatine chez des animaux normaux ou ayant reçu de la L-Dopa. Ces cellules n'ont pas de fluorescence induite à la formaldéhyde et ne sont que très faiblement argyrophiles en technique de Grimélius; elles ne réagissent pas en technique de Sevier-Munger, Hellerström-Hellman, Mac Conaill. Après administration de L-Dopa elles acquièrent und fluorescence (cellules GIC) et deviennent nettement argyrophiles en technique de Grimélius, plus faiblement en technique de Sevier-Munger. En microscopie électronique après identification immunologique sur coupe semi-fine on peut analyser les mêmes cellules sur coupes fines. Il s'agit de cellules basigranuleuses présentant, outre des grains denses difficiles souvent à distinguer de ceux des cellules G, trois structures fines caractéristiques par leur constance et leur coexistence; ce sont: des grains peu denses et homogènes—des graïns centrés par un matériel filamenteux grossier—des microfilaments nombreux. Les cellules à somatostatine semblent différentes des cellules X et D1. In normal and L-Dopa treated rabbits and mice, combined immunochemical methods, photonic histological methods for endocrine cells and ultrastructural methods were used to elucidate ultrastructure and properties of somatostatin cells of the antral mucosa. In normal rabbits, immunoreactive cells giving no fluorescence with Falck's technic, they corresponded neither to serotonin cells nor gastrin cells; they were unreactive with Fontana, Hellerström-Hellmann, Sevier-Munger and Mac Conaill methods but very slightly stained with Grimelius methods. In L-Dopa treated animals somatostatin cells gave formaldehyde induced fluorescence (they were included in GIC cells, thus in Apud group), exhibited a good reaction with Grimelius and Sevier-Munger methods. In order to carry out the alternate semi-thin/thin section procedure (semi-thin sections for immunofluorescence or immunoenzymatic detection and serial thin sections counterstained for conventional ultrastructure studies), immunological treatment were performed on M.F.F.—glutaraldehyde fixed small fragments of mucosa before inclusion in Epon 812 or, after inclusion, on semi-thin sections. We succeeded in identifying ultrastructurally somatostatin cells. They displayed round or ovoïd shaped secretory granules, and three constant typical structures: numerous microfilaments—light and homogenous granules, often seeming like lipids—granules made up by coarsely filamentous cores surrounded by a large empty halo. Somatostatin cells seemed different of X cells because of their predominant localisation in the antral mucosa (in the rabbit X cells were predominantly in the fundus) and because of the lack of nuclear microfilaments; they also seemed ultrastructuraly different of D1 cells.