Sodium chloride and water transport in the descending limb of Henle

摘要: The unique membrane characteristics of the thin descending limb Henle (DLH) play an integral part in operation countercurrent system. We examined these properties vitro by perfusing isolated limbs rabbits. Active transport NaCl was ruled out failure to demonstrate either net or transmembrane potential difference when with isosmolal ultrafiltrate same rabbit serum as bath. Transmembrane zero, and fluid -0.07 +/-0.06 nl mm(-1) min(-1), which also is not significantly different from zero. Passive permeability coefficient for Na(P(Na)) determined disappearance rate (22)Na perfusion solution. P(Na) surprisingly low, 1.61 +/-0.27 x 10(-5) cm sec(-1), a figure less than proximal convoluted tubule (PCT). Reflection (sigmaNaCl) measured Na-free raffinose solution bath sufficient added obtain conditions zero movement. sigmaNaCl 0.96 +/-0.01 greater PCT. Water osmotic gradients (L(p)) made hyperosmotic addition 100 mOsm NaCl. L(p) 1.71 +/-0.15 10(-4) ml cm(-2) sec(-1) atm(-1) 1.62 +/-0.05 atm(-1), indicating much water In each case increase osmolality collected primarily due efflux without significant influx solute. finding low sodium high consonant hypotheses that interstitial concentration Na medulla generates effective pressure results it courses through DLH abstraction entry