El-Nouty F D, Elbanna I M, Davis T P, Johnson H D
J Appl Physiol Respir Environ Exerc Physiol. 1980 Feb;48(2):249-55. doi: 10.1152/jappl.1980.48.2.249.
The effect of heat (35 degrees C) and dehydration under heat (30 h) on plasma levels of antidiuretic hormone (ADH) and aldosterone was studied on four nonpregnant dry Holstein cows. Heat exposure caused a rapid significant rise in plasma ADH without significant changes in hematocrit (Hct), small but significant increase in urine output and a significant reduction in total plasma protein. Dehydration under heat caused a sharp increase in ADH levels associated with a significant decrease in urine output and a significant increase in plasma protein, blood Hct, and serum osmolality. A significant reduction in plasma aldosterone level was observed after 24 h of heat exposure. This was associated with a slight rise in urinary sodium excretion and a significant reduction in serum sodium. Both serum and urinary potassium concentrations were significantly lower under heat. Dehydration resulted in a slow rise in aldosterone but did not reach thermoneutral level. This is probably due to the inhibitory effect of higher serum sodium observed during dehydration on plasma aldosterone secretion. The rise in ADH and decrease in aldosterone during heat exposure may explain why cattle are one of the few species that do not concentrate urine during heat exposure.
对四头未怀孕的干奶期荷斯坦奶牛研究了高温（35摄氏度）及高温下脱水（30小时）对抗利尿激素（ADH）和醛固酮血浆水平的影响。热暴露导致血浆ADH迅速显著升高，血细胞比容（Hct）无显著变化，尿量有小幅但显著增加，血浆总蛋白显著降低。高温下脱水导致ADH水平急剧升高，同时尿量显著减少，血浆蛋白、血液Hct和血清渗透压显著增加。热暴露24小时后观察到血浆醛固酮水平显著降低。这与尿钠排泄略有增加和血清钠显著降低有关。高温下血清和尿钾浓度均显著降低。脱水导致醛固酮缓慢升高，但未达到热中性水平。这可能是由于脱水期间观察到的较高血清钠对血浆醛固酮分泌的抑制作用。热暴露期间ADH升高和醛固酮降低可能解释了为什么牛是少数在热暴露期间不浓缩尿液的物种之一。
