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Response of the Distal Tubule and Cortical Collecting Duct to Vasopressin in the Rat

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Response of the Distal Tubule and Cortical Collecting Duct to Vasopressin in the Rat Response of the Distal Tubule and Cortical Collecting Duct to Vasopressin in the Rat Philip B. Woodhall, C. Craig Tisher J Clin Invest. 1973;52(12):3095-3108. https://doi.org/10.1172/JCI107509. Research Article Renal micropuncture observations in the rat suggest that the entire “distal tubule” (defined by the micropuncturist as that portion of the renal tubule extending between the macula densa and its first junction with another (renal tubule) may be responsive to vasopressin. However, this portion of the renal tubule contains two segments that are morphologically dissimilar. The “early” distal tubule is lined by epithelium characteristic of the distal convoluted tubule, while the “late” distal tubule is lined by epithelium characteristic of the cortical collecting duct. Thus, the present study was initiated to identify the most proximal site of action of vasopressin in the distal renal tubule. A water diuresis was established in rats with hereditary hypothalamic diabetes insipidus. In one-half of the animals the diuresis was interupted by an i.v. infusion of exogenous vasopressin. Morphological preservation of the kidneys was initiated after induction of vasopressin-induced antidiuresis or during maximum water diuresis. Cell swelling and dilatation of intercellular spaces, morphological findings indicative of vasopressin responsiveness, were observed in the cortical collecting duct including the late segment of the distal tubule, a segment that has also been described by morphologists as the initial collecting tubule. Morphological evidence of vasopressin-responsiveness was not observed in the early distal tubule (distal convoluted tubule). Additional morphological studies in Wistar, Long-Evans, and Sprague-Dawley rats demonstrated a marked difference […] Find the latest version: https://jci.me/107509/pdf Response of the Distal Tubule and Cortical Collecting Duct to Vasopressin in the Rat PHILIP B. WOODHALL and C. CRAIG TISHER From the Division of Nephrology, Department of Medicine and Department of Pathology, Duke University Medical Center, Durham, North Carolina 27710 A B S T R A C T Renal micropuncture observations in the late distal tubule (initial collecting tubule) and that rat suggest that the entire "distal tubule" (defined by the vasopressin-induced osmotic equilibration is a function micropuncturist as that portion of the renal tubule ex- of the latter segment alone. The findings emphasize the tending between the macula densa and its first junction importance of morphological characterization of those with another (renal tubule) may be responsive to vaso- segments of the renal tubule that are subjected to physio- pressin. However, this portion of the renal tubule contains logical investigation. two segments that are morphologically dissimilar. The "early" distal tubule is lined by epithelium characteristic of the distal convoluted tubule, while the "late" distal INTRODUCTION tubule is lined by epithelium characteristic of the corti- The distal tubule of the rat kidney, as defined by the cal collecting duct. Thus, the present study was initiated morphologist, is composed of three segments that are to identify the most proximal site of action of vasopressin histologically distinct. These include the ascending thick in the distal renal tubule. A water diuresis was estab- limb of Henle (pars recta), the macula densa (pars lished in rats with hereditary hypothalamic diabetes in- maculata), and the distal convoluted tubule (pars coni- sipidus. In one-half of the animals the diuresis was in- voluta) (1, 2). The remaining portion of the renal terupted by an i.v. infusion of exogenous vasopressin. tubule, the collecting duct, is lined by epithelium morpho- Morphological preservation of the kidneys was initiated logically distinct from that lining the convoluted portion after induction of vasopressin-induced antidiuresis or of the distal tubule (1, 2). The first portion of the cor- during maximum water diuresis. Cell swelling and tical collecting duct has been variously termed the con- dilatation of intercellular spaces, morphological findings necting portion (2) or the initial collecting tubule (3). indicative of vasopressin responsiveness, were observed The latter term will be used in this paper. In most mam- in the cortical collecting duct including the late segment malian kidneys the transition from the distal convoluted of the distal tubule, a segment that has also been de- tubule to the cortical collecting duct (i.e., the initial scribed by morphologists as the initial collecting tubule. collecting tubule) occurs well before the first junction of Mbrphological evidence of vasopressin-responsiveness one renal tubule with another; thus, the first junction of was not observed in the early distal tubule (distal con- two renal tubules is formed by two so-called initial col- voluted tubule). Additional morphological studies in lecting tubules. Wistar, Long-Evans, and Sprague-Dawley rats demon- Despite the fact that the convoluted segment of the strated a marked difference in the random availability of distal tubule (as defined morphologically) ends well be- distal convoluted tubules versus initial collecting tubules fore its first junction with another tubule, it has been potentially available for micropuncture just beneath the common practice at the micropuncture table to define renal capsule. The results suggest that hypotonic tubu- the "distal tubule" or "distal convolution" as that seg- lar fluid entering the early distal tubule (distal convoluted ment of the renal tubule that extends between the macula tubule) remains hypotonic to plasma until it enters the densa and the site of the first junction with another dis- tal tubule or distal convolution (4-7). When defined in Dr. Tisher is the recipient of Research Career Develop- this manner, it can be seen that this segment of the re- ment Award HE 440074 from the U. S. Public Health in character. Service. nal tubule is structurally heterogeneous Received for publication 30 May 197.? and in revised form Tlhtus, the "early" distal tubule of the renal micropunc- 3 August 1973. twrist is lined by epithelium characteristic of the distal The Journal of Clinical Investigation Volume 52 December 1973 3095-3108 3 09.o convoluted tubule (pars convoluta), whereas the "late" opened and the left kidney was isolated and prepared for distal tubule is lined by epithelium characteristic of the micropuncture as described previously (11). The tempera- ture of the exposed kidney was maintained by a constant intial collecting tubule. surface drip of warmed (370C) isotonic saline. Timed col- The present investigation was initiated to determine lections of urine were obtained from each separate kidney whether the structural heterogeneity of the so-called via the placement of polyethylene catheters in the left distal tubule (as defined at the micropuncture table) was ureter (P.E. 50) and the bladder (P.E. 60). Urine os- molality was measured cryoscopically with an Advanced associated with morphological evidence of functional Instruments osmometer (Advanced Instruments, Inc., Need- heterogeneity in response to the administration of exoge- ham Heights, Mass.). Experimental manipulation and/or nous vasopressin. Previous morphological studies have morphological observations were initiated when a sustained demonstrated that certain segments of the collecting water diuresis, equivalent to at least 35 p1/min/kidney, had duct of the mammalian kidney are responsive to vaso- been established. In five animals renal morphological ex- amination was carried out during water diuresis. In six pressin. In the presence of a favorable osmotic gradient, other DI rats renal tissue was fixed and prepared for that is, from the lumen to the interstitium, vasopressin- morphological examination between 6 and 60 min after induced bulk water flow across the tubular epithelium is the rapid conversion of water diuresis to antidiuresis via the associated with cell swelling and institution of a constant i.v. infusion of aqueous vasopressin dilatation of the lateral (Pitressin, Parke, Davis & Co., Detroit, Mich.) at a rate and basilar intercellular spaces. These morphological of 0.15 mU/min. changes have been observed in vivo in the medullary col- Two additional DI rats weighing 206 and 163 g, respec- lecting duct of the rat (8) and in vitro in isolated seg- tively, were studied during vasopressin administration after ments of the rabbit cortical tubule (9). Thus, these same the institution of varying degrees of water deprivation. Both of these animals were starved overnight and then morphological features were employed in the present prepared surgically as described above. One animal was study as a morphological marker to determine the most allowed free access to water before study but additional proximal site of action of vasopressin in the renal tubule fluid was not administered after the induction of anes- of the rat. The results of this investigation revealed that thesia (except for an infusion of isotonic saline at 0.02 ml/min for 40 min during surgical preparation to replace the entire cortical collecting duct (beginning with the ini- estimated surgical blood loss). The second animal was de- ial collecting tubule) was responsive to vasopressin. On prived of water for 9 h before surgery but i.v. fluids were the other hand, no evidence was found to suggest that the not given either during or after surgical preparation. distal convoluted tubule, as defined morphologically, was After surgical preparation was completed,
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