TITLE

Lanthanum permeability of tight junctions along the collecting duct of the rat

AUTHOR(S)
Tisher, C. Craig; Yarger, William E.
PUB. DATE
January 1975
SOURCE
Kidney International;Jan1975, Vol. 7 Issue 1, p35
SOURCE TYPE
Academic Journal
DOC. TYPE
Article
ABSTRACT
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 ± SE 0.63 ml/min/kg of body wt and V = 797 ± SE 108 μl/min/kg or 13.6 ± SE 2.2% of the filtered load of water. After administration of exogenous vasopressin, V fell to 311 ± 157 μl/min/kg or 5.2 ± SE 3.8% of the filtered load of water and U/Posm rose from 0.658 ± SE 0.043 to 2.124 ± 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 duet 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.
ACCESSION #
17965635

 

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