[Effects of fasting and diet resupplementation on the variation of blood zinc, copper, calcium and magnesium levels in two laboratory rodents: DBA/2 mouse and SD rat].

The effects of fasting and diet resupplementation on the variation of certain blood metals were studied in DBA/2 mice and SD rats. Metal concentrations in serum and erythrocyte were determined by atomic absorption spectrometer. Blood zinc levels were decreased and varied within sampling time from 0800 to 1200 AM, and the other blood metals concentrations were no change when animals had no fasting. After overnight fasting, blood zinc levels both in serum and erythrocyte, and erythrocyte magnesium concentration were decreased significantly. Fasting did not alter the sampling time-related variation on serum zinc levels, but would increase the erythrocyte zinc levels in opposite when in comparison with non-fasting. When animals resupplied with diet after fasting, blood zinc increased smoothly, and blood copper, calcium and magnesium would exhibit a lower concentration at the sampling time of 1400 and 1600, respectively. The species and sex did not affect the variation of blood metals levels in this study. This study showed that food intake and absorptive equilibrium of body metals had effects on the variation of blood metals concentration. Endocrine and nutrient factors also might indirectly affect this variation. So, it is suggested that a standard and compatible concern on the sampling time, animals breeding and selection should be noticed when conducting the relevant metals studies with biological samples in order to prohibit any mistakes on the explanatory results.