Nephrotic syndrome was induced in seven rats by daily aminonucleoside injections. Experiments were performed in anaesthesia 6 or 7 d later when protein loss in urine had reduced serum colloid osmotic pressure (COP) to 8.2 +/- 0.9 (SD) mmHg compared with 20.2 +/- 2.2 mmHg in controls (P < 0.01). Due to the decreased COP in the nephrotic rats, lymph flow in the main mesenteric lymphatic was 29.5 +/- 11.5 microliters min-1 compared with 4.2 +/- 2.2 microliters min-1 in the control rats (P < 0.01). The corresponding hyaluronan concentrations were 3.4 +/- 0.9 micrograms ml-1 and 12.0 +/- 3.5 micrograms ml-1, respectively (P < 0.01). Nevertheless lymphatic hyaluronan output was doubled in the nephrotic rats, but this did not affect the hyaluronan content of the small intestine of 192 +/- 58 micrograms g-1 dry wt compared with 215 +/- 69 micrograms g-1 in controls (P > 0.05). During a 20 min intravenous 0.9% saline infusion of 4 ml 100 g-1 rat, the hyaluronan concentration increased to 18.3 (6.0) micrograms ml-1 in mesenteric lymph in controls, whereas the concentration in lymph from the nephrotic rats remained unchanged. Lymphatic output increased, however, in this group as well due to the elevated flow. The amount of hyaluronan cleared daily by the main mesenteric lymphatic in awake rats corresponds to about half the tissue hyaluronan content in the drained area (østgaard & Reed 1993 b).(ABSTRACT TRUNCATED AT 250 WORDS)