Twenty-four-Hour Rhythmic Variations of Histamine in Human Female Blood

Abstract

We have previously observed that blood histamine levels undergo rhythmic 24 hour variations in male normal subjects. In the present study we examined whether similar 24 hour modifications were also present in female subjects. To this purpose, 60 healthy cycling women were enrolled for a chronobiological transverse study. To achieve experimental conditions as homogeneous as possible, the study was carried out on the first day of the menstrual flow. Histamine was determined in whole venous blood by a spectrophotofluorimetric method. The blood histamine levels showed significant rhythmic changes depending on the time of blood sampling, with 1 maximum and 1 minimum within a period of 24 h, with percentage rhythm 15.1, MESOR 0.15 μg/ml, amplitude 0.02 μg/ml and acrophase at 01:20 h. These results reveal the presence of 24 h cyclic variations of histamine levels in the female, as it occurred in male. However, the differences observed in the chronobiological rhythms of histamine between the two sexes may represent a peculiar feature of the first day of the menstrual cycle.