Chow J M, Van Kessel J A, Russell J B
Department of Animal Science, Cornell University, Ithaca, NY.
J Anim Sci. 1994 Jun;72(6):1630-5. doi: 10.2527/1994.7261630x.
Gram-negative, ionophore-resistant ruminal bacteria and Gram-positive, ionophore-sensitive species bound similar amounts of [14C]lasalocid, but neither group bound large amounts of [14C]monensin. Membrane vesicles also bound more lasalocid than monensin (P < .05). The binding was first-order at low cell or vesicle concentrations and saturable at high cell or vesicle densities. Streptococcus bovis was inhibited by both monensin and lasalocid (5 microM), but cells that were re-incubated in medium lacking ionophore grew rapidly. Lasalocid-treated cells grew very slowly when they were resuspended in fresh medium. Based on these results, it seemed that lasalocid had a higher affinity for bacterial membranes than monensin. Mixed bacteria, however, bound nearly equal amounts of [14C]monensin and [14C]lasalocid (P > .05). Monensin binding was greatly reduced when the mixed ruminal bacteria were pretreated with Tris+EDTA (P < .05), but Tris+EDTA did not affect the binding of lasalocid. Mixed ruminal protozoa always took up more lasalocid than monensin (P < .05), but feed particles bound equal amounts of [14C]lasalocid and [14C]monensin (P > .05). Based on the binding capacity of mixed ruminal bacteria, ruminal protozoa, and feed particles, there would be little free ionophore in ruminal fluid.
革兰氏阴性、对离子载体耐药的瘤胃细菌以及革兰氏阳性、对离子载体敏感的细菌结合的[14C]拉沙洛西数量相似，但两组结合的[14C]莫能菌素都不多。膜囊泡结合的拉沙洛西也比莫能菌素多（P < 0.05）。在低细胞或囊泡浓度下，结合呈一级反应，在高细胞或囊泡密度下可饱和。牛链球菌受到莫能菌素和拉沙洛西（5 microM）的抑制，但在缺乏离子载体的培养基中重新培养的细胞生长迅速。用拉沙洛西处理过的细胞重新悬浮在新鲜培养基中时生长非常缓慢。基于这些结果，似乎拉沙洛西对细菌膜的亲和力比莫能菌素高。然而，混合细菌结合的[14C]莫能菌素和[14C]拉沙洛西数量几乎相等（P > 0.05）。当用Tris + EDTA预处理混合瘤胃细菌时，莫能菌素的结合大大减少（P < 0.05），但Tris + EDTA不影响拉沙洛西的结合。混合瘤胃原生动物摄取的拉沙洛西总是比莫能菌素多（P < 0.05），但饲料颗粒结合的[14C]拉沙洛西和[14C]莫能菌素数量相等（P > 0.05）。基于混合瘤胃细菌、瘤胃原生动物和饲料颗粒的结合能力，瘤胃液中几乎不会有游离离子载体。
