Reports describe various biochemical events associated with hypoxia. Hypoxic conditions demonstrate effects on erythrocyte production by bone marrow, cerebral injury, tumors, vascular cells (vascular tone, endothelial permeability and growth factors, coagulant functions), and free radical production.
The delivery of oxygen to the cells of tissues is a function of hemoglobin concentration, hematocrit, oxygen content of the red cells, extraction of oxygen by the tissues, and metabolism by intervening cells (10).Erythropoiesis is a process involving cell divisions followed by a loss of nuclei, mitochondria, and ribosomes. An important aspect of this process is protein synthesis, particularly globin. A known regulatory mediator of erythropoiesis is erythropoietin (Epo), which is produced mostly in the kidneys; a principal stimulus for this synthesis is tissue hypoxia. An increase in erythrocytes production by bone marrow, leading to an increase in red cell mass, is found in chronic hypoxic conditions such as high altitudes. This is not a beneficial process. Studies with human subjects are limited; predominant erythroid cells found in the bone marrow associated with chronic hypoxia are normoblasts (advanced degree of differentiation).
Pinder and Smits report that increases in hematocrit (a tube with graded markings used to determine the volume of packed red cells in a blood specimen by centrifugation) are found in humans at high altitude, because of plasma volume loss over the first few days of acclimation (8). Rivera, Leon-Velarde, Huicho, and Monge studied hypoxic rats and found the following: protein concentrations in the bone marrow was higher in hypoxics; blood hemoglobin increased in parallel to protein concentration in the bone marrow (9).
Hayakawa, Terashima, Kayukawa, Ohta, and Okada studied men with obstructive sleep apneas to investigate changes in cerebral tissue oxygenation and blood volume. Nocturnal hypoxi...