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Splenic contraction-induced reversible increase in hemoglobin concentration in intermittent hypoxia
I Kuwahira1, U Kamiya, T Iwamoto
1Department of Medicine, Tokai University School of Medicine, Isehara, Kanagawa 259-1193, Japan.
Journal of Applied Physiology (Bethesda, Md. : 1985)
|January 14, 1999
Summary
Intermittent hypoxia (IHx) causes a temporary rise in blood hemoglobin, especially after 4 days. This increase is linked to spleen contraction and alpha2-adrenoreceptor activity, offering oxygen supply benefits without sustained polycythemia.
Area of Science:
- Physiology
- Cardiovascular Science
- Respiratory Medicine
Background:
- Intermittent hypoxia (IHx) can cause polycythemia, but transient changes in hemoglobin during IHx are less understood.
- Investigating short-term hemoglobin regulation during IHx is crucial for understanding oxygen transport adaptations.
Purpose of the Study:
- To determine if IHx causes a transient increase in blood hemoglobin concentration ([Hb]) in rats.
- To elucidate the mechanisms, including splenic contraction and adrenergic receptor involvement, behind this [Hb] change.
Main Methods:
- Rats were exposed to intermittent hypoxia (10% O2, 1 h/day) for up to 5 weeks.
- Experiments involved splenectomy, plasma catecholamine measurements, and alpha-adrenoreceptor blockade/stimulation.
- Hemoglobin concentration ([Hb]) was measured to assess changes.
Main Results:
- A reversible increase in [Hb] was observed after 4 days of IHx, but not in controls or after shorter IHx periods.
- Splenectomy abolished the IHx-induced [Hb] increase.
- Alpha2-adrenoreceptor blockade prevented the [Hb] rise, while stimulation increased [Hb] in IHx rats.
Conclusions:
- IHx induces a transient, reversible [Hb] increase during hypoxia mediated by splenic contraction.
- This response is dependent on enhanced alpha2-adrenoreceptor sensitivity.
- This mechanism may improve oxygen delivery during hypoxia without the risks of chronic polycythemia.