Neocytolysis on Descent from Altitude: A Newly Recognized Mechanism for the Control of Red Cell Mass

17 April 2001 | Volume 134 Issue 8 | Pages 652-656

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.

Objectives: 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.

Design: Prospective observational and interventional study.

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

Participants: Nine volunteers with polycythemia.

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

Measurements: Changes in red cell mass, hematocrit, hemoglobin concentration, reticulocyte count, ferritin level, serum erythropoietin, and enrichment of administered ¹³C 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. ¹³C 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 ¹³C-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.

Author and Article Information

From Baylor College of Medicine, Houston, Texas, and Universidad Peruana Cayetano Heredia, Lima, Peru.

Acknowledgments: The authors thank the following persons for essential technical and logistic support: Bertha Mendoza, Ruben Morcial Albiyor, Hortencia Carmelo, Mary Moir, Robert Talamini, Dr. Henry van Dyk, Dr. Holly van Dyk, and John Moulds. They also thank the volunteer participants for their cooperation.

Grant Support: By National Aeronautics and Space Administration grants NAGW 4993 and NASA/NSBRI NCC9-58.

Requests for Single Reprints: Lawrence Rice, MD, 6565 Fannin, MS 902-Main, Houston, TX 77030; e-mail, lrice{at}bcm.tmc.edu.

Current Author Addresses: Drs. Rice and Alfrey, Ms. Driscoll, and Mr. Whitley: Section of Hematology, Department of Medicine, Baylor College of Medicine, 6565 Fannin, MS 902-Main, Houston, TX 77030.

Drs. Ruiz and Gonzales and Ms. Tapia: Instituto de Investigaciones de la Altura, and Department of Physiological Sciences, Universidad Peruana Cayetano Heredia, Lima 1843, Peru.

Dr. Hachey: Department of Pharmacology, Vanderbilt University, 2201 West End Avenue, Nashville, TN 37232-6400.

Author Contributions: Conception and design: L. Rice, W. Ruiz, T. Driscoll, G.F. Gonzalez, C.P. Alfrey.

Analysis and interpretation of the data: L. Rice, T. Driscoll, C.E. Whitley, C.P. Alfrey.

Drafting of the article: L. Rice.

Critical revision of the article for important intellectual content: L. Rice, W. Ruiz, D.L. Hachey, G.F. Gonzalez, C.P. Alfrey.

Final approval of the article: L. Rice, W. Ruiz, T. Driscoll, C.E. Whitley, R. Tapia, D.L. Hachey, G.F. Gonzalez, C.P. Alfrey.

Provision of study materials or patients: W. Ruiz, R. Tapia, G.F. Gonzalez.

Statistical expertise: T. Driscoll.

Obtaining of funding: L. Rice, C.P. Alfrey.

Administrative, technical, or logistic support: W. Ruiz, T. Driscoll, C.E. Whitley, R. Tapia, D.L. Hachey, G.F. Gonzalez.

Collection and assembly of data: L. Rice, W. Ruiz, T. Driscoll, C.E. Whitley, R. Tapia, D.L. Hachey, C.P. Alfrey.