Carbon dioxide effects on erythropoietin and erythropoiesis

The addition of carbon dioxide during a short bout (6 to 24 hr) of hypoxia suppresses the production of Ep. The effects of carbon dioxide on Ep production and erythropoiesis were determined in hypoxic rats over a 6-day period. Carbon dioxide suppressed both renal and extrarenal Ep production induced by hypoxia. However, rats exposed to a hypoxic environment with 5% CO2 became as polycythemic as rats exposed to the same hypoxia without CO2. This may result from the following. (1) A factor other than Ep is involved in stimulating erythropoiesis in these animals. (2) The large amount of Ep produced during hypoxia is in excess, and only a small amount is needed to compensate for the hypoxia by producing increased numbers of RBCs. (3) A significant degree of hemoconcentration occured, resulting in the increased number of RBCs observed.