Circadian Variation of the Phagocytic Activity of Polymorphonuclear Leukocytes and of Various Other Parameters in 13 Healthy Male Adults

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Abstract
Twenty-four different laboratory parameters including the phagocytic activity (phagocytic index) of polymorphonuclear leukocytes (PMNs) and various hematologic variables were investigated in 13 young healthy men during Spring 1988 in Munich, Germany. Venous blood of these volunteers was obtained under standardized conditions at 4-h intervals over a 24-h span. All parameters were analyzed by the single cosinor method and by a Kruskal-Wallis analysis of variance (ANOVA). Statistically significant circadian rhythms were found for the number of circulating lymphocytes and leukocytes (WBCs), potassium, systolic blood pressure, phagocytic index, Quick test, heart rate, and rectal body temperature (p less than 0.05; single cosinor). For all of these parameters except WBCs, rectal body temperature, and Quick test, a temporal variation was confirmed by the ANOVA (p less than 0.05; phagocytic index: p = 0.05). The circadian acrophases of WBC, number of circulating lymphocytes, and phagocytic index were all found at about 01:00 h. This temporal coincidence of the acrophases of the phagocytic index and the number of circulating lymphocytes may reflect the modulation of phagocytosis by T lymphocytes that release cytokines known to stimulate the phagocytic activity of PMNs.