Albumin excretion by the kidney: the effects of osmotic diuresis.

Urine albumin excretion rate in female Sprague-Dawley rats was measured duing a stable period of normal hydration and following mannitol-induced osmotic diuresis. Mannitol infusion resulted in a significant increase in urine volume and fractional excretion of sodium, but glomerular filtration rate, albumin excretion rate, and the sieving coefficient for albumin remained stable. The results suggest that under physiological conditions, changes in albumin excretion are dependent upon changes in glomerular filtration rather than urine flow.