Resting plasma and salivary IL-6 concentrations are not correlated in distance runners
Measurement of IL-6 has been widely undertaken to examine inflammatory and immune responses to exercise. Use of salivary IL-6 offers an alternative to the invasive collection procedures required for IL-6 measurement in plasma samples. Rarely, however, has the degree of association between plasma and salivary IL-6 been reported. The aim of the current study was to investigate the relationship between resting salivary and plasma IL-6 concentrations in 45 trained distance runners (36 males, 9 females; age: 35.1 ± 8.0 y, mean ± SD). Plasma and saliva samples were collected from athletes under resting conditions. Plasma IL-6 concentrations were determined using a Bioplex suspension array system and commercially available reagents. Salivary IL-6 concentrations were determined using a commercially available high-sensitivity ELISA kit. At rest, the mean (± SD) plasma IL-6 concentration was 3.43 ± 3.75 pg mL−1 compared to a mean salivary IL-6 concentration of 1.80 ± 4.25 pg mL−1. IL-6 concentrations in plasma and saliva samples were not correlated (r = −0.031, p = 0.85). At rest, salivary IL-6 concentrations do not reflect plasma IL-6 concentrations. The potential for salivary IL-6 to act as a surrogate marker for plasma IL-6 responses when examining inflammatory and immune responses to exercise, therefore, appears unlikely.
KeywordsCytokines Immunity Athletes Exercise
The authors gratefully acknowledge the participation of the athletes in this study. This study was funded by a research grant from the Australian Institute of Sport.
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