Proteinuria in relation to age-dependent changes in the plasma and urine concentrations of some electrolytes and hematological indices in Wistar rats

The study was carried out to determine the influence of proteinuria on plasma and urine concentrations of electrolytes and hematological indices in Wistar rats of different age groups. Eighty Wistar rats of both sexes were used for this study. Groups 1 and 2 each consisted of 8 one month old male and female rats; 3 and 4 had 8 three month old rats; 5 and 6 had 8 six month old rats; 7 and 8 had 8 nine month old rats; 9 and 10 had 8 twelve month old rats. The plasma sodium, potassium and calcium concentrations of 3 month old rats were significantly lower when compared with 1, 6, 9 and 12 months of age. Similarly, rats aged 3 months had significantly lower urine concentrations of sodium, potassium and calcium than rats of other age groups. A strong correlation was observed between the urine protein and urine sodium of the female rats at ages 3, 9 and 12 months but it was only significant at age 12 months (p = 0.105 and p = 0.021, respectively). Also, the female rats aged 3 and 12 months had a strong correlation between their urine protein and urine calcium (p = 0.002 and p = 0.131, respectively). The red blood cells, lymphocyte and monocyte counts of the rats increased gradually and peaked at age 9 months with a subsequent decline at 12 months of age. It was concluded that the influence of proteinuria on electrolytes was least observed in the rats aged 3 months, since they had reduced and consistent plasma and urine concentrations of electrolytes measured when compared with other age groups. This implies that long-term renal studies involving the use of rats must be carefully interpreted because of the changes in plasma and urine concentrations of electrolytes as the rats age.