The role of the light/dark cycle in the daily rhythm of serum proteins in Equus caballus

This research was carried out on five clinically healthy Sella Italiana horses to determine the daily rhythm oftotal proteins and their fractions, to establish if these rhythms are endogenously generated and to assess therole of light as synchroniser of these rhythms. Blood samples were collected from each subject every 3 h overa period of 48 h, starting at 9:00 on day 1 and finishing at 9:00 on day 3, into vacutainer tubes without ananticoagulant via intravenous cannulas inserted into the jugular vein. Total serum proteins, albumin, α1-, α2-,β1-, β2- and γ-globulin concentrations were assessed in all samples. The application of two-way ANOVAshowed a significant effect of the time of day on total proteins, albumin, β1- and β2-globulins, and of theexperimental conditions on total proteins α1-, α2-, β1-, β2- and γ-globulins. No statistical modifications wereobserved on the A/G ratio. Daily rhythmicity was exhibited only by total proteins and albumin during the L/Dcycle. We can claim that the fluctuation of serum total proteins and albumin concentrations are daily and notcircadian and that they are driven by the L/D cycle.