Rabinowitz L, Gunther R A
Pflugers Arch. 1975;353(4):349-60. doi: 10.1007/BF00587031.
The possibility of uphill transport of urea from the collecting ducts of sheep fed diets containing 14% protein (HP) and 4.9% protein (LP) was explored by measuring cortex to papilla and urine to papilla gradients of urea during ethacrynic acid diuresis. Clearance studies were done on adult, unanesthetized, hydropenic, vasopressin infused sheep. Saline was given to compensate for urine loss during ethacrynic acid diuresis. Following a period of antidiuresis, ethacrynic acid administration caused and increase in fractional water excretion to 0.33 (HP) and 0.44 (LP), an increase in fractional sodium excretion to 0.28 (HP) and 0.41 (LP), and an average increase in glomerular filtration rate of 14.7%. Fractional potassium excretion showed no consistent change. Renal concentrating ability and medullary sodium accumulation were inhibited. Antidiuretic LP and HP medullary urea accumulation patterns were lost. However, identical but small ascending cortex to papilla urea gradients remained in the LP and HP animals. There was no significant difference between the urea concentration in urine and papilla tissue water. The results fail to provide support for the presence of active urea transport from the collecting ducts of sheep fed high or low protein diets.
通过在速尿利尿期间测量皮质到乳头以及尿液到乳头的尿素梯度，探讨了给摄入含14%蛋白质（高蛋白组，HP）和4.9%蛋白质（低蛋白组，LP）日粮的绵羊的集合管中尿素进行上坡转运的可能性。对成年、未麻醉、禁水、输注血管加压素的绵羊进行了清除率研究。在速尿利尿期间给予生理盐水以补偿尿液损失。在一段抗利尿期后，给予速尿导致水排泄分数增加至0.33（HP）和0.44（LP），钠排泄分数增加至0.28（HP）和0.41（LP），肾小球滤过率平均增加14.7%。钾排泄分数没有一致变化。肾浓缩能力和髓质钠蓄积受到抑制。抗利尿的LP和HP组髓质尿素蓄积模式消失。然而，LP和HP组动物中从皮质到乳头存在相同但较小的尿素梯度上升。尿液和乳头组织水中的尿素浓度之间没有显著差异。结果未能支持在摄入高蛋白或低蛋白日粮的绵羊的集合管中存在活跃的尿素转运。
