Kuwahira I, Kamiya U, Iwamoto T, Ishii M, Moue Y, Ohta Y, Gonzalez NC
Department of Medicine, Tokai University School of Medicine, Isehara, 259-1193, Kanagawa, Japan
Pathophysiology. 2000 Sep;7(3):165-169. doi: 10.1016/s0928-4680(00)00047-x.
We have previously shown that intermittent hypoxia (IHx, 10% O(2), 60 min/day) leads to an increase in the splenic alpha2-adrenoceptor response and results in a splenic contraction-induced reversible increase in hemoglobin concentration ([Hb]). In the present study, we determined whether IHx of shorter duration (15 min/day (15-min) and 30 min/day (30-min)), produced this phenomenon in rats. A significant increase in [Hb] during hypoxia was observed in both the groups, but its magnitude was larger in the 30-min IHx rats. Even when the cumulative exposure time (time/dayxdays) was shorter, the [Hb] increase was larger in the rats with longer daily hypoxic exposure. The alpha2-adrenoceptor antagonist yohimbine abolished the [Hb] increase of 15- and 30-min IHx. The increase in [Hb] following administration of the alpha2-adrenoceptor agonist oxymetazoline was also higher in 30-min IHx; indicating that the higher [Hb] produced by longer daily hypoxic exposure times is the result of increases in alpha2-adrenergic-receptor response of greater magnitude. In conclusion, IHx for periods as short as 15 and 30 min/day increases the splenic alpha2-adrenoceptor response and its magnitude reaches the maximum value depending on the daily hypoxic exposure time. A reversible increase in [Hb] constitutes a useful mechanism that protects organ oxygen supply during hypoxic episodes of variable duration and intensity.
我们之前已经表明，间歇性低氧（IHx，10%氧气，每天60分钟）会导致脾脏α2 -肾上腺素能受体反应增强，并导致脾脏收缩引起血红蛋白浓度（[Hb]）可逆性升高。在本研究中，我们确定了较短持续时间（每天15分钟（15 - min）和每天30分钟（30 - min））的IHx是否会在大鼠中产生这种现象。在两个组中均观察到低氧期间[Hb]显著升高，但在30分钟IHx组中升高幅度更大。即使累积暴露时间（每天时间×天数）较短，每日低氧暴露时间较长的大鼠中[Hb]升高幅度更大。α2 -肾上腺素能受体拮抗剂育亨宾消除了15分钟和30分钟IHx引起的[Hb]升高。在30分钟IHx组中，给予α2 -肾上腺素能受体激动剂羟甲唑啉后[Hb]的升高也更高；这表明每日较长低氧暴露时间产生的较高[Hb]是α2 -肾上腺素能受体反应更大幅度增加的结果。总之，每天15分钟和30分钟的IHx会增加脾脏α2 -肾上腺素能受体反应，其幅度取决于每日低氧暴露时间并达到最大值。[Hb]的可逆性升高构成了一种有用的机制，可在不同持续时间和强度的低氧发作期间保护器官的氧气供应。
