Kuwahira I, Kamiya U, Iwamoto T, Moue Y, Urano T, Ohta Y, Gonzalez N C
Department of Medicine, Tokai University School of Medicine, Isehara, Kanagawa 259-1193, Japan.
J Appl Physiol (1985). 1999 Jan;86(1):181-7. doi: 10.1152/jappl.1999.86.1.181.
The effect of intermittent hypoxia (IHx) on blood hemoglobin concentration ([Hb]) and the underlying mechanisms were studied in rats exposed to 10% O2, 1 h/day, for up to 5 wk. IHx protocols with longer daily hypoxic exposure show persistent polycythemia; however, it is unknown whether [Hb] increases transiently during hypoxia in protocols without polycythemia. Hypoxia produced a reversible [Hb] increase after 4 days of IHx but not in normoxic controls (NxC) or after shorter period of IHx. Splenectomy abolished the phenomenon. Plasma epinephrine and norepinephrine levels during hypoxia were comparable in IHx and NxC groups, but the epinephrine-induced [Hb] increase was larger in IHx. The alpha1- and alpha2-adrenoreceptor blockade (phentolamine) and alpha2-blockade (yohimbine) abolished the [Hb] increase of IHx rats. Conversely, alpha2-receptor stimulation (oxymetazoline) increased [Hb] during normoxia in IHx but not in NxC. In conclusion, this IHx protocol results in reversible [Hb] increases during hypoxia via splenic contraction mediated by increased alpha2-adrenoreceptor response. This may protect O2 supply during hypoxia without the cardiovascular burden of polycythemia during normoxia.
在每天暴露于10%氧气、持续1小时、长达5周的大鼠中，研究了间歇性低氧（IHx）对血液血红蛋白浓度（[Hb]）的影响及其潜在机制。每日低氧暴露时间更长的IHx方案会导致持续性红细胞增多症；然而，在无红细胞增多症的方案中，[Hb]在低氧期间是否会短暂增加尚不清楚。低氧在IHx 4天后导致[Hb]可逆性增加，但在常氧对照组（NxC）或较短时间的IHx后未出现这种情况。脾切除消除了该现象。低氧期间，IHx组和NxC组的血浆肾上腺素和去甲肾上腺素水平相当，但肾上腺素诱导的[Hb]增加在IHx组中更大。α1和α2肾上腺素能受体阻断剂（酚妥拉明）和α2阻断剂（育亨宾）消除了IHx大鼠的[Hb]增加。相反，α2受体激动剂（羟甲唑啉）在常氧期间使IHx组的[Hb]增加，但在NxC组中未出现这种情况。总之，该IHx方案通过α2肾上腺素能受体反应增加介导的脾脏收缩，在低氧期间导致[Hb]可逆性增加。这可能在低氧期间保护氧气供应，而在常氧期间不会带来红细胞增多症的心血管负担。
