Chronic intermittent hypoxia induces hypoxia‐evoked catecholamine efflux in adult rat adrenal medulla via oxidative stress

• DOI: 10.1113/jphysiol.2006.112524
• Publication Date: 2006-06-16T00:56:36Z
• Authors: Ganesh K. Kumar; Vandana Rai; Suresh D. Sharma; Devi Prasadh Rama...; Ying‐Jie Peng; Dangjai Souvannak...; Nanduri R. Prabhakar
• Keywords: Hypoxia; Intermittent hypoxia; Corticosterone

Chronic intermittent hypoxia (CIH) augments physiological responses to low partial pressures of O2 in the arterial blood. Adrenal medullae from adult rats, however, are insensitive direct effects acute hypoxia. In present study, we examined whether CIH induces hypoxic sensitivity rat adrenal medulla and, if so, by what mechanism(s). Experiments were performed on male rats exposed (15 s 5% followed 5 min 21% O2; 9 episodes h(-1); 8 h d(-1); for 3 or 10 days) comparable, cumulative durations continuous (CH; 4 7% 20 1 days). Noradrenaline (NA) and adrenaline (ADR) effluxes monitored ex vivo medullae. CIH, evoked robust NA ADR effluxes, whereas these absent control those CH days. Hypercapnia (10% CO2; either acidic, pH 6.8, isohydric, 7.4) was ineffective eliciting catecholamine (CA) efflux control, rats. Nicotine (100 microM) this response abolished but not Systemic administration 2-deoxyglucose depleted content attenuated response, indicating downregulation neurally regulated CA secretion. Cytosolic mitochondrial aconitase enzyme activities decreased medullae, suggesting increased generation superoxide anions. antioxidants reversed effect medulla. Rats exhibited blood elevated plasma CA, responses. These observations demonstrate that sensing via mechanisms involving anions suggest hypoxia-evoked contributes, part, pressure CA.