Parker A J, Hamlin G P, Coleman C J, Fitzpatrick L A
Australian Institute of Tropical Veterinary and Animal Science, School of Biomedical Sciences, James Cook University, Townsville 4811, Australia.
J Anim Sci. 2003 Feb;81(2):512-9. doi: 10.2527/2003.812512x.
The effect on water and electrolyte balance of stress, simulated by intravenous infusion of cortisol, was studied using 24 18-mo-old Merino wethers (37.0 +/- 0.94 kg mean body weight [BW]) over 72 h. The sheep were allocated to one of four groups: 1) no water/no cortisol (n = 6); 2) water/no cortisol (n = 4); 3) no water/cortisol (n = 6); and 4) water/cortisol (n = 4). Animals allocated to the two cortisol groups were given 0.1 mg x kg BW(-1) x h(-1) of hydrocortisone suspended in isotonic saline to simulate stress for the duration of the experiment. Total body water, plasma cortisol, osmolality and electrolytes, and urine electrolytes were determined at 24-h intervals for 72 h. In the presence of cortisol, total body water was maintained in the face of a water deprivation insult for 72 h. Water deprivation alone did not induce elevated plasma concentrations of cortisol, in spite of a 13% loss of total body water between 48 and 72 h. Infusion of cortisol was found to increase urine output (P = 0.003) and decrease total urinary sodium output (P = 0.032), but had no effect on plasma electrolyte levels or water intake. Water deprivation was found to increase plasma sodium concentrations (P = 0.037). These results indicate that sheep given cortisol to simulate stress suffer from a loss of body water in excess of that associated with a loss of electrolytes, and support the hypothesis that elevated physiological concentrations of cortisol induce a diuresis in ruminants that contributes to dehydration.
通过静脉输注皮质醇模拟应激对水和电解质平衡的影响，在72小时内对24只18月龄的美利奴阉羊（平均体重[BW]为37.0±0.94千克）进行了研究。将绵羊分为四组之一：1）无水/无皮质醇（n = 6）；2）有水/无皮质醇（n = 4）；3）无水/皮质醇（n = 6）；4）有水/皮质醇（n = 4）。分配到两个皮质醇组的动物在等渗盐水中给予0.1毫克×千克体重（-1）×小时（-1）的氢化可的松，以在实验期间模拟应激。在72小时内每隔24小时测定全身水、血浆皮质醇、渗透压和电解质以及尿液电解质。在存在皮质醇的情况下，面对72小时的缺水损伤，全身水得以维持。尽管在48至72小时之间全身水损失了13%，但仅缺水并未导致血浆皮质醇浓度升高。发现输注皮质醇会增加尿量（P = 0.003）并减少尿钠总排出量（P = 0.032），但对血浆电解质水平或水摄入量没有影响。发现缺水会增加血浆钠浓度（P = 0.037）。这些结果表明，给予皮质醇以模拟应激的绵羊所遭受的身体水分流失超过了与电解质流失相关的水分流失，并支持了以下假设：生理浓度升高的皮质醇会在反刍动物中诱导利尿，从而导致脱水。
