Hamburger R J, Lawson N L, Schwartz J H
Am J Physiol. 1976 Feb;230(2):286-90. doi: 10.1152/ajplegacy.1976.230.2.286.
Previous investigations have suggested that there is a functional heterogeneity along the length of the proximal convoluted tubule. This study was designed to confirm and extend these suggestions by examining the intrinsic absorption of fluid and the effect of parathyroid hormone (PTH) on net fluid absorption in isolated, anatomically defined segments of rabbit superficial proximal tubules. The EPCT (early proximal convoluted tubule), LPCT (late proximal convoluted tubule), and PR (pars recta) segments were studied under controlled conditions by the isolated perfused tubule technique. In 23 EPCT, base-line fluid absorption was 1.38 +/- 0.04 (SE), a rate significantly higher than those of 11 LPCT (0.62 +/- 0.02; P less than 0.001) and 12 PR (0.52 +/- 0.03 nl mm-1 min-1, P less than 0.001) segments. In 10 EPCT, mean control fluid absorption was 1.31 +/- 0.04 nl mm-1 min-1; addition of PTH resulted in a decrease to 0.95 +/- 0.05 nl mm-1 min-1 (P less than 0.001); and, after removal of PTH, fluid absorption increased (P less than 0.001). Parathyroid hormone had no effect on either seven LPCT segments or six PR segments. These results demonstrate differences in intrinsic capacity to absorb fluid by anatomically defined segments of the rabbit proximal tubule. This functional heterogeneity is further supported by the observed differential response to PTH by the various anatomic segments of the proximal tubule.
以往的研究表明，近端曲管全长存在功能异质性。本研究旨在通过检测兔浅表近端小管解剖学界定的分离节段中液体的内在吸收以及甲状旁腺激素（PTH）对净液体吸收的影响，来证实并扩展这些观点。采用分离灌注小管技术，在受控条件下研究了早期近端曲管（EPCT）、晚期近端曲管（LPCT）和直部（PR）节段。在23个EPCT节段中，基线液体吸收为1.38±0.04（SE），该速率显著高于11个LPCT节段（0.62±0.02；P<0.001）和12个PR节段（0.52±0.03 nl mm-1 min-1，P<0.001）。在10个EPCT节段中，平均对照液体吸收为1.31±0.04 nl mm-1 min-1；添加PTH导致吸收减少至0.95±0.05 nl mm-1 min-1（P<0.001）；去除PTH后，液体吸收增加（P<0.001）。甲状旁腺激素对7个LPCT节段或6个PR节段均无影响。这些结果表明，兔近端小管解剖学界定的节段在液体吸收的内在能力上存在差异。近端小管各解剖节段对PTH的不同反应进一步支持了这种功能异质性。
