Browsing by Autor "A. Lemoine"

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    Comparative responses of arterial oxygen saturation and heart rate during postnatal development in rats living at high and low altitude.
    (Wiley, 2013) A. Lemoine; Gabriella Villalpando; Marcelino Gonzales; Rudy Soria; Vincent Joseph
    We used pulse oximetry to measure arterial oxygen saturation (SpO2) and heart rate (HR) in 4 and 14 day‐old rats raised at HA (La Paz, Bolivia, 3,600 m/12,000ft) or at sea level (SL, Québec, Canada). SpO2 and HR were measured at 5 different levels of inspired PO2 (PiO2: 160 ‐ 60 mmHg – 10 min each), in awake rats maintained in a chamber flushed with room air or the desired gas mixtures. When exposed to a PiO2 of 160 mmHg, P4 HA rats had a similar SpO2 than P4 SL, but a lower HR. At lower PiO2, HA rats maintained a much higher SpO2 than SL rats. HR increased in HA rats (but not in SL rats) at low PiO2. Contrastingly, P14 HA rats exposed to a PiO2 of 160 mmHg had a lower SpO2 than SL (93.7±1.1% vs. 98.8±0.1%, p<0.0001), and similar SpO2 at lower PiO2. HR was higher in P14 HA rats vs. SL rats at all PiO2 levels. A group of SL rats was raised in hypoxia (13.5% O2 – similar to HA PiO2) between P4 and P14. This reduces SpO2 values measured at PiO2 below 160 mmHg, and enhances HR. Male and female rats had similar responses. We conclude that: a) 4‐day old rats raised at HA had efficient responses that help maintaining a high SpO2 under a wide range of PiO2 ‐ b) these responses are no longer apparent in P14. Since rats are not found under natural conditions at HA, success to develop adequate responses to hypoxia during early postnatal development might be critical for genetic adaptation to altitude. Founded by NSERC.
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    Life-long consequences of postnatal normoxia exposure in rats raised at high altitude
    (American Physiological Society, 2011) Delphine Lumbroso; A. Lemoine; Marcelino Gonzales; Gabriela Villalpando; Tommy Seaborn; Vincent Joseph
    We tested the hypothesis that exposure of high-altitude (HA) rats to a period of postnatal normoxia has long-term consequences on the ventilatory and hematological acclimatization in adults. Male and female HA rats (3,600 m, Po 2 ≃ 100 Torr; La Paz, Bolivia) were exposed to normal room air [HA control (HACont)] or enriched oxygen (32% O 2 ; Po 2 ≃ 160 Torr) from 1 day before to 15 days after birth [HA postnatal normoxia (HApNorm)]. Hematocrit and hemoglobin values were assessed at 2, 12, and 32 wk of age. Cardiac and lung morphology were assessed at 12 wk by measuring right ventricular hypertrophy (pulmonary hypertension index) and lung air space-to-tissue ratio (indicative of alveolarization). Respiratory parameters under baseline conditions and in response to 32% O 2 for 10 min (relieving the ambient hypoxic stimulus) were measured by whole body plethysmography at 12 wk. Finally, we performed a survival analysis up to 600 days of age. Compared with HACont, HApNorm rats had reduced hematocrit and hemoglobin levels at all ages (both sexes); reduced right ventricular hypertrophy (both sexes); lower air space-to-tissue ratio in the lungs (males only); reduced CO 2 production rate, but higher oxygen uptake (males only); and similar respiratory frequency, tidal volume, and minute ventilation. When breathing 32% O 2 , HApNorm male rats had a stronger decrease of minute ventilation than HACont. HApNorm rats had a marked tendency toward longer survival throughout the study. We conclude that exposure to ambient hypoxia during postnatal development in HA rats has deleterious consequences on acclimatization to hypoxia as adults.