title: The threshold of the intermittent hypoxic exposure period to elicit polycythemia in rats.
abstract: It is not yet clear whether there is an intermittent hypoxia (IHx) threshold to elicit polycythemia and blood pressure elevation, and whether blood hemoglobin concentration ([Hb]) increases with an increase in the hypoxic exposure period. We have previously shown that repetitive exposure to 10% O2 for 60 min/day for up to 5 weeks does not produce polycythemia. In the present study, we evaluated the effect of IHx of 10% O2, 120 min/day for 1, 2, 3 and 4 weeks on [Hb], arterial blood pressure, heart rate and arterial blood gases in the rat. IHx of 10% O2, 120 min/day induced polycythemia at 1 week and produced a time-dependent increase in [Hb] from 0 week to 4 weeks. Arterial blood pressure significantly increased during IHx exposure for 4 weeks probably due to a combination of an increased sympathetic activity as well as increased blood viscosity. The IHx threshold for polycythemia might exist between 60 min/day and 120 min/day in this level of hypoxia.
authors.affiliation: Department of Medicine, Tokai University Tokyo Hospital, 1-2-5 yoyogi, Shibuya-ku, Tokyo 151-0053, Japan.
authors.forename: Tokuzen
authors.initials: T
authors.lastname: Iwamoto
authors.forename: Uguri
authors.initials: U
authors.lastname: Kamiya
authors.forename: Makoto
authors.initials: M
authors.lastname: Ishii
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Urano
authors.forename: Ichiro
authors.initials: I
authors.lastname: Kuwahira
mesh_terms: D000818:Animals; D001794:Blood Pressure / Q000502:physiology; D006339:Heart Rate / Q000502:physiology; D006454:Hemoglobins / Q000378:metabolism; D000860:Hypoxia; D008297:Male; D011086:Polycythemia / Q000503:physiopathology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013997:Time Factors
chemical_list: D006454:Hemoglobins