Extended exposure to low pO2
A custom designed pO2 modulation chamber (7 star
systems, Delhi, India) was used. A constant temperature (25±5 ˚C) and
relative humidity (50±5%) were maintained in the simulation chamber
during experiments. Airflow of 2 L/min was provided to Sprague-Dawley
(SD) rats undergoing hypobaric hypoxia exposure. The animals were
provisioned with food and water ad libitum during the entire
duration of low pO2 exposure. Age and gender matched
male SD rats were exposed to either normoxia (n=5) or low
pO2 of 8.19 kPa (equivalent altitude: 7620 m;
simulated). Exposure lasted for 3 days (HD3), 7 days (HD7) and 14 days
(HD14) (n=5 per group) of stay in the pO2 chamber. The
rate of decrease of PB was ~4.1 kPa/min.
Exposure to PB 40 kPa (pO2 8.19 kPa)
began after 12 h each at PB 71 kPa and
PB 59 kPa. The purpose of such a slow and graded low
pO2 exposure was to minimize mortality of animals and
mimic real-world conditions of altitude ascent. After the completion of
normal and low pO2 exposures, the animals were
sacrificed and their lungs and plasma collected. Further, quantitative
proteomics investigations, biochemical assays, assessment of redox
specific transcripts and validations using immuno-chemical methods were
performed on these. All animals were sacrificed using approved
procedures to minimize pain and suffering immediately after the
exposure. Our study design was initially approved by the Institute’s
Animal Ethics Committee (Fig. 1).