Influence of the way of reporting alpha-Amylase values in saliva in different naturalistic situations: A pilot study

Abstract

The objective of this pilot study was to compare the different ways of measuring salivary alpha-amylase (sAA, enzymatic vs. concentration) and to evaluate the influence that the different ways of reporting the results can have in sAA interpretation. For this purpose, sAA was measured by direct quantification and also by an enzymatic assay in three different naturalistic situations, a physical stressor (situation 1) and two mental stressors of different intensity (situations 2 and 3). The results were expressed in three different ways (without correction, multiplied by flow rate and divided by protein concentration). sAA concentration and activity increased just after situations 1 and 3. When values were multiplied by the flow rate, significant changes after situation 1 were detected only for sAA activity but not for sAA concentration, being these changes of lower significance and magnitude that those observed for sAA activity without any correction. In addition, a significant increase in sAA activity was found at T+15 in situation 2. In situation 3 the significant decrease in sAA at T+15 disappeared. When values were divided by protein concentration, there were no significant changes in situations 1 or 3, but a decrease in situation 2 at T+0 and an increase at T+15. sAA activity and concentration showed a significant correlation in all situations. This pilot study points out that the way of expressing sAA can influence the results obtained in different stress models and also their interpretation. Therefore, how sAA is reported and the factors involved in the different ways of expressing sAA, should be taken into consideration for an objective interpretation of sAA values.

Fig 1. Salivary flow rate (left) and salivary total protein (right) in the three situations expressed as log transformed (ln x = ln(x + 1)).

(A) A final football indoor match (situation 1), five minutes before match (T-0) and five minutes after match (T+0); (B) an academic activity consisted of the resolution of clinical cases (situation 2), just before (T-0), just after (T+0) and fifteen minutes after (T+15) practice; (C) an activity collecting pig’s blood (situation 3), at least fifteen minutes before (T-0), just after (T+0) and fifteen minutes after (T+15) the collection. Graphs show means ± Standard deviation (SD). Asterisks indicate significant post-hoc difference (Fisher LSD test): * P<0.05; ** P<0.01; *** P<0.001.

Fig 2. Different ways to express salivary alpha-amylase (sAA) concentration (upper graph) and activity (lower graph) in three biological situations expressed as log transformed (ln x = ln(x + 1)).

(A) A final football indoor match (situation 1), five minutes before match (T-0) and five minutes after match (T+0); (B) an academic activity consisting of the resolution of clinical cases (situation 2), just before practice (T-0), just after (T+0) and fifteen minutes after (T+15) practice; (C) an activity collecting pig’s blood (situation 3), at least fifteen minutes before (T-0), just after (T+0) and fifteen minutes after (T+15) the collection. Graphs show means ± Standard deviation. Asterisks indicate significant post-hoc difference (Fisher LSD test): * P<0.05; ** P<0.01; *** P<0.001.

Fig 3. Linear regression of correlation plots.

A correlation study was made to compare sAA enzymatic activity with quantification by fluorometry in three situations consisting of an indoor football match (A) or situation 1, a clinical cases practice (B) or situation 2 and a blood collecting activity (C) or situation 3. r = Spearman r-value.