酪酸が成めん羊の第一胃粘膜の組織構造におよぼす影響 Influence of Butyrate on the Microscopic Structure of Ruminal Mucosa in Adult Sheep

成反芻家畜の第一胃粘膜の組織構造におよぼす酪酸の影響を調べるために,成めん羊の第一胃前房の第一胃じゅう毛を生検して光顕的,電顕的に検索した.絶食下に29/kg体重/日のn-酪酸ナトリウムを,毎日正午に第一胃内へ急速投与すると,第一胃粘膜は,上皮細胞分裂像の増加,上皮下小静脈の拡張,上皮脚の発達,上皮細胞の配列異常,上皮基底細胞の大小不同,上皮内の変性細胞の増加,上皮角質化細胞層の消失,基底層細胞の小器管の有糸分裂に伴うと思われる変化,等の変化を示した.対照として,同量のn-酪酸ナトリウムを緩速投与した場合や,0.9%および2.65%の食弱塩水を投与した場合の第一胃じゅう毛を観察した.これらの場合の第一胃粘膜の組織は,2.65%食塩水投与区における上皮下毛細血管の拡張と,上皮細胞間隙の拡張とを除けば,既報の絶食時の成めん羊での組織像と同様の所見を示した.このように,酪酸は成めん羊の第一胃粘膜の組織にかなりの変化をおこさせるが,この変化は酪酸の増殖促進効果と密接に関連すると思われる.酪酸の組織構造に対する作用は,細胞増殖に対する作用と同様に,1日あたりの投与量よりも,投与による第一胃内の酪酸濃度の上昇によって規定されると考えられ,かつ,絶食条件下では一過性の作用で,上記の変化は投与を続けたにもかかわらず,回復する傾向にあった.

Ruminal papillae were biopsied from four groups of fasted adult sheep intraruminally given 2g/kg body weight/day of sodium n-butyrate rapidly or slowly and the same amount of 2.65% or 0.9% saline daily. The cross sections of the papillae were observed with light and elecron microscopes. The administration of butyrate involved the following changes in the ruminal mucosa: frequent mitosis of epithelial cells, dilation of sub-epithelial venules, development of epithelial pegs, appearance of larger basal cells, irregular arrangement of epithelial cells, increase in the degenerating and/or degenerated epithelial cells, disappearance of cornified layers at the surface of the epithelium, and many typical figures of the basal cell organella in and around the mitosis. Samples of three other groups of sheep showed the figures of untreated fasted sheep already reported, except for the dilation of sub-epithelial capillaries found in the case of 2.65% saline administration. Changes involved by butyrate are considered to be closely related to the mitogenic effect of the acid and was involved by the elevated intraruminal concentration rather than the total amount of the acid given in a day. They tended to regress under fasting condition, though further administrations of butyrate were carried on.