Splenic contraction-induced reversible increase in hemoglobin
concentration in intermittent hypoxia.
Kuwahira, Ichiro, Uguri Kamiya, Tokuzen Iwamoto, Yoshihiro Moue,
Tetsuya Urano, Yasuyo Ohta and Norberto C. Gonzalez.
1Department of Medicine, Tokai University School of Medicine,
Isehara, Kanagawa 259-1193, Japan and 2Department of Molecular and
Integrative Physiology, University of Kansas Medical Center, Kansas
City, KS 66160-7401, USA
APStracts 5:0412A, 1998.
The effect of intermittent hypoxia (IHx) on blood hemoglobin
concentration ([Hb]), and the underlying mechanism, were studied in
rats exposed to 10% O2, 1 h/day for up to 5 weeks. 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 IHx. Splenectomy abolished the phenomenon. Plasma
epinephrine and norepinephrine levels during hypoxia were comparable
in IHx and NxC, but the epinephrine-induced [Hb] increase was larger
in IHx. _1- and _2-adrenoreceptor blockade (phentolamine) and _2
-blockade (yohimbine) abolished the [Hb] increase of IHx. Conversely,
_2-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 _2-adrenoreceptor response. This
may protect O2 supply during hypoxia without the cardiovascular
burden of polycythemia during normoxia.
Received 10 July 1998; accepted in final form 14 September 1998.
APS Manuscript Number A621-8.
Article publication pending Journal of Applied Physiology.
ISSN 1080-4757 Copyright 1998 The American Physiological Society.
Published in APStracts on 12 November 1998