Hare J E, Tesarowski D B, Dawe G E, Vlaminck K, Shewen P E, Viel L
Department of Biomedical Sciences, Ontario Veterinary College, University of Guelph, Canada.
Am J Vet Res. 1996 Jul;57(7):1034-9.
To evaluate a 5-hydroxytryptamine type-2 receptor antagonist, metrenperone (MET), in alleviating respiratory distress associated with experimentally induced Pasteurella haemolytica pneumonia in feedlot calves.
Double-blind controlled clinical trial.
30 healthy 6- to 8-month-old Hereford-type calves (250 to 450 kg).
Initial measurements were made of rectal temperature (RT), arterial blood gas (ABG) tensions, and pulmonary mechanics. Calves were then infected with P haemolytica in logarithmic phase of growth by intratracheal inoculation. 18 hours later, determination of RT and ABG tensions, and pulmonary function testing were repeated and calves were selected for inclusion in the study on the basis of having 2 of the following: respiratory rate > 50 breaths/min, RT > 40 C, or PaO2 > 20 mm of Hg below the baseline value. MET (0.1 mg/kg of body weight, IM) or an equivalent vehicle dose was then administered. RT, ABG, and pulmonary mechanics measurements were repeated at 0.5, 1, 2, 3, 4, 6, 12, and 24 hours after treatment. Calves were then euthanatized, and gross necropsy scoring and histologic examination were performed on the lungs.
Infection with P haemolytica caused significant increases in RT and respiratory rate, and reduction in PaO2, PaCO2, and tidal volume 18 hours after inoculation. MET-treated calves and significantly reduced rectal temperature between 1 and 12 hours, compared with vehicle-treated calves. In addition, MET-treated calves had reduced respiratory rate with concomitantly increased tidal volume between 0.5 and 2 hours after treatment, compared with vehicle-treated calves. Necropsy revealed acute lobar bronchopneumonia in all 30 calves, but there was no difference in necropsy score between treatment groups.
MET may have an antipyretic effect on calves with pneumonia caused by P haemolytica. Its influence on pulmonary mechanics was minimal however, and it did not induce lung lesions in the short term.
评估5-羟色胺2型受体拮抗剂美坦色林（MET）对缓解育肥牛实验性诱导的溶血巴氏杆菌肺炎相关呼吸窘迫的作用。
双盲对照临床试验。
30头健康的6至8月龄赫里福德型犊牛（体重250至450千克）。
首先测量直肠温度（RT）、动脉血气（ABG）张力和肺力学指标。然后通过气管内接种对数生长期的溶血巴氏杆菌感染犊牛。18小时后，再次测定RT和ABG张力，并进行肺功能测试，根据以下两项指标将犊牛纳入研究：呼吸频率>50次/分钟、RT>40℃或动脉血氧分压（PaO2）比基线值低>20毫米汞柱。随后给予MET（0.1毫克/千克体重，肌肉注射）或等量的赋形剂剂量。治疗后0.5、1、2、3、4、6、12和24小时重复测量RT、ABG和肺力学指标。然后对犊牛实施安乐死，并对肺部进行大体尸检评分和组织学检查。
接种溶血巴氏杆菌18小时后，感染导致RT和呼吸频率显著增加，PaO2、二氧化碳分压（PaCO2）和潮气量降低。与给予赋形剂的犊牛相比，MET治疗的犊牛在1至12小时之间直肠温度显著降低。此外，与给予赋形剂的犊牛相比，MET治疗的犊牛在治疗后0.5至2小时之间呼吸频率降低，同时潮气量增加。尸检显示所有30头犊牛均有急性大叶性支气管肺炎，但治疗组之间的尸检评分无差异。
MET可能对溶血巴氏杆菌引起的犊牛肺炎有解热作用。然而，其对肺力学的影响极小，且在短期内未诱发肺部病变。
