Papillary plasma flow in rats. I. Relation to urine osmolality in normal and Brattleboro rats with hereditary diabetes insipidus.

Papillary plasma flow (PPF) was measured by the albumin accumulation technique in rats of the Brattleboro strain with or without diabetes insipidus (DI and HZ respectively) and in Wistar rats. Measurements were also performed in DI rats receiving antidiuretic hormone for 30 min or 5 days and in dehydrated Wistar rats. PPf in HZ control and Wistar control rats was similar to previously published measurements. In contrast PPF was significantly higher in DI rats (461 +/- 26 microliters/min . g versus 263 +/- 28 in HZ) and decreased significantly after acute ADH administration. It returned to control values after prolonged ADH administration (262 +/- 40). Plasma flow entering the papilla was inversely correlated with urine osmolality up to 1000 mosmol/kg H2O. Further increases in urine concentration (dehydration of Wistar rats) did not modify further PPF (255 +/- 28 versus 270 +/- 16 in non dehydrated Wistar). PPF might be influenced indirectly by ADH or prostaglandins and seems to depend on the osmotic environment of the papilla up to a certain limit. The factors which maintain PPF at a given minimum level with further increases in urine concentration are not known.