Neocytolysis on descent from altitude: a newly recognized mechanism for the control of red cell mass.
BACKGROUND
Studies of space-flight anemia have uncovered a physiologic process, neocytolysis, by which young red blood cells are selectively hemolyzed, allowing rapid adaptation when red cell mass is excessive for a new environment.


OBJECTIVE
1) To confirm that neocytolysis occurs in another situation of acute plethora-when high-altitude dwellers with polycythemia descend to sea level; and 2) to clarify the role of erythropoietin suppression.


METHODS
Prospective observational and interventional study.


METHODS
Cerro de Pasco (4380 m) and Lima (sea level), Peru.


METHODS
Nine volunteers with polycythemia.


METHODS
Volunteers were transported to sea level; three received low-dose erythropoietin.


METHODS
Changes in red cell mass, hematocrit, hemoglobin concentration, reticulocyte count, ferritin level, serum erythropoietin, and enrichment of administered(13)C in heme.


RESULTS
In six participants, red cell mass decreased by 7% to 10% within a few days of descent; this decrease was mirrored by a rapid increase in serum ferritin level. Reticulocyte production did not decrease, a finding that establishes a hemolytic mechanism.(13)C changes in circulating heme were consistent with hemolysis of young cells. Erythropoietin was suppressed, and administration of exogenous erythropoietin prevented the changes in red cell mass, serum ferritin level, and(13)C-heme.


CONCLUSIONS
Neocytolysis and the role of erythropoietin are confirmed in persons with polycythemia who descend from high altitude. This may have implications that extend beyond space and altitude medicine to renal disease and other situations of erythropoietin suppression, hemolysis, and polycythemia.
Rice
L
L
Section of Hematology, Department of Medicine, Baylor College of Medicine, 6565 Fannin, MS 902-Main, Houston, TX 77030, USA. lrice@bcm.tmc.edu
Ruiz
W
W
Driscoll
T
T
Whitley
C E
CE
Tapia
R
R
Hachey
D L
DL
Gonzales
G F
GF
Alfrey
C P
CP
D000222:Adaptation, Physiological; D000328:Adult; D000531:Altitude; D002452:Cell Count; D004912:Erythrocytes / Q000166:cytology*; D004921:Erythropoietin / Q000097:blood / Q000627:therapeutic use; D005293:Ferritins / Q000097:blood; D006400:Hematocrit; D006454:Hemoglobins / Q000378:metabolism; D006461:Hemolysis / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D011086:Polycythemia / Q000188:drug therapy / Q000503:physiopathology; D011446:Prospective Studies; D012156:Reticulocytes / Q000166:cytology
D006454:Hemoglobins; D004921:Erythropoietin; D005293:Ferritins