Proximal tubular function in XXXX with thoracic caval constriction.

@entity235 @entity1372 @entity4295
The effect of saline infusion on proximal @entity1372 reabsorption was compared in normal @entity235 and in @entity235 with acute or chronic partial thoracic vena cava obstruction. After acute vena cava obstruction, proximal fractional @entity1372 reabsorption rose by 74%. During continued caval obstruction, saline loading strikingly reduced proximal reabsorption but @entity1372 excretion remained minimal. In chronic caval @entity235 , saline loading reduced proximal fractional @entity1372 reabsorption by 31% but @entity1372 excretion in the micropunctured kidney was only 41 muEq/min. After saline infusion in normal @entity235 , proximal fractional @entity1372 reabsorption fell 39% while unilateral @entity1372 excretion rose to 584 muEq/min. Nephron filtration rate was also measured before and after saline loading in normal and chronic caval @entity235 in both repunctured and fresh tubules. There was a marked increase in nephron filtration rate in repunctured tubules and no change in freshly punctured tubules in both groups. The effect of saline loading on nephron filtration rate in normal and chronic caval @entity235 was similar, therefore, whether repunctured or fresh @entity4295 were considered.We conclude that saline infusion depresses proximal @entity1372 reabsorption in acute and chronic TVC @entity235 . Since saline loading markedly increases distal delivery without a concomitant natriuresis, enhanced distal reabsorption must play a major role in the @entity1372 retention exhibited by chronic caval @entity235 . Redistribution of filtrate does not appear to be a factor in this @entity1372 retention.
