Effect of starvation on biochemical indices of renal function in the rat

The effect of starvation on urinary output and biochemical indices of renal function was investigated in rats. Starvation resulted in a marked fall in water intake. Urinary output paradoxically increased during the first day following starvation, but fell dramatically thereafter. Urinary creatinine excretion and creatinine clearance fell markedly, but plasma creatinine concentration did not alter. Plasma urea concentration and urinary urea excretion fell. Plasma sodium concentration increased, whilst plasma potassium concentration did not alter; urinary sodium and potassium excretion fell. Plasma bicarbonate concentration fell marginally, but the anion gap increased to a greater extent. Following re-feeding, water intake and urine output increased, as did urinary creatinine excretion and creatinine clearance. Plasma urea and urinary urea concentrations, as well as sodium and potassium excretion, increased. Plasma bicarbonate increased and the anion gap decreased. These indices improved within 2 days of re-feeding and were restored to normal in 5 days.