Salivary α‐amylase as a measure of endogenous adrenergic activity

Abstract

SUMMARY. This investigation was designed to evaluate the production rates and concentrations of salivary a‐amylase as a measure of adrenergic activity under several conditions of stress in human subjects. Saliva and blood samples were simultaneously collected from men at four 15 min intervals both before and after regimens for exercise, a written examination, or a rest period. The regressions of salivary a‐amylase on plasma norepinephrine (NE) concentrations were significant for both exercise (P < 0–001) and examination (P < 0.01) protocols. Aerobic exercise induced a 3‐fold mean increase in a‐amylase; both NE and epinephrine (EP) increased ≅5‐fold over control levels. Levels of a‐amylase and NE returned to control levels within 30.45 min after exercise, but EP remained elevated by ≅2‐fold during the remaining hour of observation. During the written examination, α‐amylase and NE, but not EP, concentrations increased in parallel. In further studies the effects of exercise and exposure to heat and cold on the relationship of salivary a‐amylase to heart rate and body temperature were investigated. Greater intensities of exercise were associated with greater increases in a‐amylase concentrations. During heat exposure in a sauna (66 ° C for 40 min) amylase, heart rate and body temperature all increased progressively. However, during exposure to cold (4 ° C for 40 min) amylase increased rapidly, though heart rate and body temperature remained unchanged. Salivary Cortisol concentrations were unchanged during exposure to heat or cold. We conclude that salivary a‐amylase concentrations are predictive of plasma catecholamine levels, particularly NE, under a variety of stressful conditions, and may be a more direct and simple end point of catecholamine activity than are changes in heart rate.