Methods After 1 to 2 weeks on a low sodium chloride diet (sodium chloride, 0.5 Eq/g) with free access to water and food, male Sprague-Dawley rats weighing between 100 and 150 g were anesthetized with ip mactin (Promonta, Hamburg, West Germany), 100 mg/kg of body wt. Small rats were chosen for study because the BJP used in the study was limited in availability and was administered in a dose graded for weight. A low sodium chloride diet was used in all studies to ensure uniform sodium chloride intake and excretion prior to study. Following trache-ostomy, polyethylene catheters (PE-50) were placed in the jugular vein for maintenance, inulin, and test-substance infu-sion, in the femoral artery for collecting blood samples and monitoring blood pressure, and in the bladder for collecting urine samples under oil in preweighed vials. Animals were placed on a heated table, and rectal temperature was main-tained between 36.5 and 38 C.

Clearance studies. Polyfructosan 2%(mutest, Laevosan-Gesellschaft, Linz/Donau) in 0.15 M sodium chloride was given at a rate of 1 ml/100 g body wt per hour throughout the study. A 60-mm equilibration period was followed by a 45-to 60-mm control clearance period, a 120-mm test infusion period, another 60-mm equilibration period, and finally a 30-to 45-mm experimental clearance period. Arterial hematocrit was deter-mined at the beginning and the end of each period. Inulin clearance, urinary flow rate, osmolality, and sodium concentra-tion were determined during the control and experimental clearance periods. Serum protein concentration was estimated at the beginning and the end of the infusion period in groups 1, 4, M, and L (see below). Urinary protein excretion was determined during the infusion period in groups 1, 2, 4, M, and L. Protein electrophoresis and a Putnam test were performed on urine collected from groups 1, 3, and 4 during the infusion period.