Dyke T M, Sams R A, Hinchcliff K W
Analytical Toxicology Laboratory, College of Veterinary Medicine, The Ohio State University, Columbus 43210-1089, USA.
Am J Vet Res. 1998 Nov;59(11):1481-7.
To determine the effects of acute exercise on hepatic blood flow by studying hepatic clearance of bromsulphalein for several submaximal exercise intensities.
8 adult Standardbred mares.
Horses were subjected to 4 submaximal exercise intensities (resting and 40, 60, and 80% maximal oxygen consumption). After horses had been running at the required treadmill speed for 1 minute, bromsulphalein (BSP; 5 mg/kg of body weight, IV) was administered during a 45- to 60-second period, and horses continued at the desired speed for an additional 15 minutes. Blood samples were collected at 2-minute intervals for 30 minutes, and plasma concentration of BSP was determined by spectrophotometry. Estimates of pharmacokinetic variables were compared among the 4 exercise intensities, using a Friedman repeated-measures analysis on ranks and linear regression.
Median values for clearance of BSP from blood and plasma decreased significantly with exercise and was linearly related to exercise intensity. Exercise-induced differences were not detected in the volume of distribution of BSP. Elimination half-life of BSP increased significantly with increasing exercise intensity and was linearly related to exercise intensity.
Acute submaximal exercise has a dramatic effect on clearance of BSP in horses. Presumably, exercise-induced decreases in splanchnic blood flow limit blood flow to the liver, decreasing hepatic clearance of BSP and leading to persistence of plasma concentrations of BSP.
Drugs that are efficiently extracted by the liver may have decreased hepatic clearance when horses exercise at submaximal intensities.
通过研究不同次最大运动强度下溴磺酚酞的肝清除率来确定急性运动对肝血流量的影响。
8匹成年标准赛马母马。
让马匹进行4种次最大运动强度（静息状态以及最大耗氧量的40%、60%和80%）的运动。在马匹以所需跑步机速度奔跑1分钟后，在45至60秒内静脉注射溴磺酚酞（BSP；5毫克/千克体重），然后马匹继续以期望速度奔跑15分钟。每隔2分钟采集血样，共采集30分钟，通过分光光度法测定血浆中BSP的浓度。使用Friedman秩重复测量分析和线性回归比较4种运动强度下的药代动力学变量估计值。
血液和血浆中BSP的清除率中位数随运动显著降低，且与运动强度呈线性相关。未检测到运动强度对BSP分布容积的影响。BSP的消除半衰期随运动强度增加而显著增加，且与运动强度呈线性相关。
急性次最大运动对马匹体内BSP的清除有显著影响。推测运动引起的内脏血流量减少限制了肝脏的血流量，降低了肝脏对BSP的清除率，导致血浆中BSP浓度持续存在。
当马匹以次最大强度运动时，肝脏高效摄取的药物其肝清除率可能会降低。
