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The aim of the present study was to test the hypothesis that glutathione peroxidase, uric acid, and a number of hematological biomarkers do not vary in adult mares, over a 24-hour period. Seven adult (age 10 ± 6 yrs; weight 370 ± 30 kg) Arabian Purebred mares were used. Blood samples were collected every two hours, except during the period after-meals, when samples were collected every 30 minutes, totaling four samples in two hours. These samples were used to analyze glutathione peroxidase (GPx), uric acid (UA), glucose (GLU), total plasma protein (TPP), red blood cells (RBC), hemoglobin (HB), hematocrit (HT), red cell distribution width (RDW), white blood cells (WBC) and lymphocytes (LYM). One-way repeated measures analysis of variance (ANOVA) was used to determine significant differences. Tukey’s test was used for multiple comparisons between the averages. Ρ values < 0.05 were considered statistically significant. Antioxidant biomarkers GPx and UA, as well as hematological biomarkers TPP, RBC, HB and HT exhibited a diurnal rhythm that was not affected by food ingestion, while RDW-SD, RDW-CV, WBC and LYM did not present a statistically significant change in the same period.
Nuclear receptors such as pregnane X
receptor (PXR) and constitutive androstane receptor (CAR) regulate the transcription
of transporter and cytochrome P450 (CYP). The diurnal variation was observed in
some transporters regulated by nuclear receptors. We investigated whether
diurnal variation in PXR and CAR exists in mice. We also examined the effect of
food intake on the diurnal rhythm of hepatic PXR and CAR using fed and fasted
mice. In liver and small intestine of fed mice, the mRNA levels of PXR and CAR
were unchanged between 7:00 AM and 7:00 PM. In contrast to fed mice, fasting
mice partly exhibited the diurnal variation in PXR, not in CAR. The mRNA levels
of PXR at 7:00 AM were significantly higher than that those at 7:00 PM in liver
of fasting mice. These results indicated the different effects of fasting in mice
on diurnal variation of PXR in each tissue.