Renal Hilar Lymph: Effects of Diuresis on Flow and Composition in Dogs

Renal lymph was collected from single hilar lymphatics in 58 anesthetized dogs (1) to study the mechanism by which lymph production is affected during diuresis and (2) to determine whether a medullary contribution to renal lymph could be defined by changes in the electrolyte concentration of hilar lymph with concomitant alterations in the concentration gradient of the renal medulla. When diuresis was induced by a solute load (mannitol), lymph flow increased by 25 to 300%. On the other hand, when diuresis was induced without such a solute load, lymph flow was either unaffected (mersalyl) or slightly reduced (furosemide). It was concluded that the effect of mannitol on renal lymph flow was mediated primarily through its general effect on extracellular fluid rather than through any specific intrarenal consequence of the diuresis itself.Control hilar lymph-to-plasma concentration ratios for Na (1.057 ± 0.040), Cl (1.129 ± 0.040) and Ca (0.770 ± 0.046) but not K (0.0986 ± 0.086) were found to be significantly different from 1.0. Failure of mannitol diuresis to alter significantly the lymph-plasma ratios of Na and Cl provided evidence that the high electrolyte concentrations of the inner medulla were not reflected in hilar lymph. The finding that furosemide abolished the lymph-plasma concentration difference for Na and significantly reduced that for Cl was taken as evidence that the outer medulla was a significant source of renal hilar lymph.