Tisher C C, Yarger W E
Kidney Int. 1975 Jan;7(1):35-44. doi: 10.1038/ki.1975.5.
The permeability of the tight junctions (zonulae occludentes) was evaluated along the entire length of the collecting duct of the rat using a lanthanum tracer technique. Nine rats with hereditary hypothalamic diabetes insipidus were studied using standard micropuncture and clearance techniques. Glomerular filtration rate (GFR) estimated from inulin clearance, urine and plasma osmolality (U/Posm) and urine flow rate (V) were determined in eight of nine animals. During either sustained diuresis (five animals) or vasopressin-induced antidiuresis (four animals), individual surface convolutions of distal convoluted tubules or early cortical collecting ducts were preserved for ultrastructural examination by intraluminal microperfusion with a glutaraldehyde-formaldehyde fixative followed by a second microperfusion with a lanthanum tracer. Mean GFR during diuresis was 6.31 plus or minus se 0.63 ml/min/kg of body wt and v=797 plus or minus se 108 mul/min/kg or 13.6 plus or minus se 2.2% of the filtered load of water. After administration of exogenous vasopressin, V fell to 311 plus or minus 157 mul/min/kg or 5.2 plus or minus se 3.8% of the filtered load of water and U/Posm rose from 0.658 plus or minus se 0.043 to 2.124 plus or minus 0.454. Tight junctions of cortical and outer medullary segments of the collecting duct resisted lanthanum penetration. Tight junctions of the inner medullary and papillary segments of the collecting duct were freely permeable to lanthanum suggesting the presence of a paracellular shunt pathway for solute and water movement. The results were independent of the presence or absence of vasopressin. Physiological studies have previously demonstrated that cortical and outer medullary segments of the collecting duct have a low urea permeability while inner medullary and papillary segments of the collecting duct have a relatively high urea permeability. The possibility is suggested that urea movement across the inner medullary and papillary segments of the collecting duct may occur, at least in part, via a paracellular pathway formed by the nonoccluding tight junction and the lateral intercellular space.
采用镧示踪技术，沿着大鼠集合管的全长评估紧密连接（闭锁小带）的通透性。使用标准微穿刺和清除技术对9只遗传性下丘脑性尿崩症大鼠进行研究。在9只动物中的8只中测定了由菊粉清除率估算的肾小球滤过率（GFR）、尿和血浆渗透压（U/Posm）以及尿流率（V）。在持续性利尿（5只动物）或血管加压素诱导的抗利尿（4只动物）期间，通过用戊二醛 - 甲醛固定剂进行管腔内微灌注，随后用镧示踪剂进行第二次微灌注，保存远曲小管或早期皮质集合管的单个表面卷曲用于超微结构检查。利尿期间的平均GFR为6.31±标准误0.63 ml/min/kg体重，V = 797±标准误108 μl/min/kg或滤过水负荷的13.6±标准误2.2%。给予外源性血管加压素后，V降至311±157 μl/min/kg或滤过水负荷的5.2±标准误3.8%，U/Posm从0.658±标准误0.043升至2.124±0.454。集合管皮质段和外髓段的紧密连接可抵抗镧的穿透。集合管内髓段和乳头段紧密连接对镧可自由通透，提示存在溶质和水移动的细胞旁分流途径。结果与血管加压素的有无无关。生理学研究先前已表明，集合管皮质段和外髓段对尿素的通透性较低，而集合管内髓段和乳头段对尿素的通透性相对较高。有人提出，尿素穿过集合管内髓段和乳头段的移动可能至少部分通过由非封闭性紧密连接和细胞间外侧间隙形成的细胞旁途径发生。
