Ventilatory response to acute hypoxia in transgenic mice over-expressing erythropoietin: effect of acclimation to 3-week hypobaric hypoxia.

We used transgenic mice constitutively over-expressing erythropoietin ("tg6" mice) and wild-type (wt) mice to investigate whether the high hematocrit (hct), consequence of Epo over-expression affected: (1) the normoxic ventilation (V (E)) and the acute hypoxic ventilatory response (HVR) and decline (HVD), (2) the increase in ventilation observed after chronic exposure to hypobaric hypoxia (430mmHg for 21 days), (3) the respiratory "blunting", and (4) the erythrocythemic response induced by chronic hypoxia exposure. V (E) was found to be similar in tg6 and wt mice in normoxia (FIO2=0.21).

Optimal hemoglobin concentration and high altitude: a theoretical approach for Andean men at rest.

The beneficial role of erythrocytosis for O2 transport has been questioned by evidence from bloodletting and hemodilution research as well as by studies suggesting the existence of an "optimal" hematocrit (Hct) or hemoglobin concentration ([Hb]) value. To assess to what extent erythrocytosis is beneficial in Andean men at high altitude, we examined and discussed optimal [Hb] using a mathematical approach by modeling the mixed (mean) venous Po2 (Pv(O2)) and arterial O2 content, considering for both the relation between [Hb] and arterial Po2. Relations of [Hb] to other physiological variables such as cardiac output and convective arterial O2 transport were also discussed, revealing the importance of Pv(O2) in this model.