P. CherdrungsiMahidol University2018-06-142018-06-141989-01-01Aviation Space and Environmental Medicine. Vol.60, No.4 (1989), 329-331009565622-s2.0-0024589934https://repository.li.mahidol.ac.th/handle/20.500.14594/15749Experiments were undertaken with rats to determine the effects of chronic exposure to a simulated high altitude of 5,000 m on phagocytic activity of the reticuloendothelial system (RES). Phagocytic index (K) was determined by measuring the rate of blood clearance of colloidal carbon given intravenously. K value of the chronically altitude exposed rats was found to be greater than that of the sea level control animals (p < 0.02), indicating that acclimatization to high altitude stimulated the RES phagocytosis. On analysis of the weights of the liver and spleen, the corrected phagocytic index (α) of the high altitude-acclimatized rats was also found to be higher than that of the sea level control animals (p < 0.05) while the weights of the liver and spleen expressed in percent body weight were not affected by high altitude exposure. The increased number of carbon-containing Kupffer cells in the liver and the increased phagocytic indices (both K and α values) suggested that most of the increase in RES phagocytic activity was due to increased RES tissue activity per unit mass of tissue rather than tissue hypertrophy.Mahidol UniversityEnvironmental ScienceMedicineArticleSCOPUS