AGING AND MARROW NEUTROPHIL RESERVES

Objectives: Measurement of blood neutrophil (PMN) counts after the adm inistration of hydrocortisone, granulocyte colony-stimulating factor ( G-CSF) and epinephrine. Design: Prospective study, with subjects servi ng as their own controls before and after administration of hydrocorti sone, G-CSF, and epinephrine. Setting: The G-CSF and hydrocortisone st udies were conducted at the Clinical Research Center, University of Wa shington, and the epinephrine study was conducted at the Seattle VA Me dical Center. Participants: Healthy volunteers of both sexes (ages 20 to 30 years and 70 to 80 years) were recruited from the community. The subjects had no acute or chrome medical problems and were on no presc ription medications. Main Outcome Measures: Change in the blood PMN co unt after administration of hydrocortisone (25 and 200 mg intravenousl y), G-CSF (30 and 300 mug subcutaneously), or epinephrine (10, 25, and 50 ng/kg/min intravenously). Results: Baseline PMN counts, were simil ar for all comparison groups. The peak PMN response (maximum count-bas eline count) to hydrocortisone was significantly less in the older sub jects (P < 0.01) at both doses. The peak PMN responses were 4588 +/- 4 18/mm3 (25 mg) and 6906 +/- 1121/mm3 (200 mg) in the young and 1886 +/ - 399/mm3 (25 mg) and 2387 +/- 372/mm3 (200 mg) in the elderly subject s. The peak PMN response following G-CSF was not different (P > 0.05) in the two groups at both the dosages: 6696 +/- 736/mm3 (30 mug) and 9 801 +/- 893/mm3 (300 mug) in the young and 6340 +/- 833/mm3 (30 mug) a nd 9733 +/- 956/mm3 (300 ug) in the elderly. There was no age-related change in the response to epinephrine. Conclusions: Aging has no effec t on baseline PMN counts, bone marrow PMN reserves as measured with G- CSF, and blood PMN pools as measured with epinephrine. However the abi lity to mobilize these PMNs from the marrow into blood, as measured by the hydrocortisone response, is significantly reduced in the elderly.