Effect of adrenal enucleation on inner medullary collecting duct function in the rat

1982 ◽  
Vol 242 (5) ◽  
pp. F453-F456
Author(s):  
H. H. Bengele ◽  
E. A. Alexander
Keyword(s):  
Sodium Chloride ◽  
Collecting Duct ◽  
Potassium Excretion ◽  
Collection Site ◽  
Salt Load ◽  
Inner Medullary Collecting Duct ◽  
Impaired Ability ◽  
Potassium Secretion ◽  
Medullary Collecting Duct ◽  
And Control

After adrenal enucleation rats have an impaired ability to excrete a salt load. From micropuncture studies comparing data obtained from the late distal collection site and the urine, it has been suggested that this antinatriuretic effect occurs along the collecting duct. These studies are indirect, however, and cannot evaluate the contribution of deep nephrons. We have performed studies directly measuring inner medullary collecting duct (IMCD) function in saline-loaded rats 6 days after adrenal enucleation (AE). The fraction of filtered fluid, sodium, chloride, and potassium was analyzed as a function of IMCD length. In six AE rats 35% of the fluid, 35% of the sodium, and 31% of the chloride delivered to the IMCD was reabsorbed. In six saline-loaded control rats, however, no statistically significant net reabsorption of fluid sodium, or chloride was detected. Net potassium secretion along the IMCD was found in both AE and control rats. No difference between groups was noted, and net addition accounted for 17% of the potassium excreted. We conclude that after AE, the excretion of fluid, sodium, and chloride is impaired during saline expansion because of enhanced reabsorption along the IMCD. AE does not affect potassium handling along the IMCD or potassium excretion.

Potassium secretion along the inner medullary collecting duct

1979 ◽  
Vol 236 (3) ◽  
pp. F278-F282
Author(s):  
H. H. Bengele ◽  
E. R. McNamara ◽  
E. A. Alexander
Keyword(s):  
Linear Regression ◽  
Collecting Duct ◽  
Potassium Transport ◽  
Sham Operation ◽  
Potassium Excretion ◽  
Inner Medullary Collecting Duct ◽  
Potassium Secretion ◽  
Medullary Collecting Duct ◽  
The Difference

Potassium transport along the inner medullary collecting duct (IMCD) was evaluated by the microcatheterization technique in Charles River CD (cesarean derived) rats 7-9 days after sham operation (S) or uninephrectomy (UNPX). The fraction of filtered potassium (TF/P)K/In) as a function of IMCD length was analyzed by linear regression. In 13 S rats there was a significant correlation and slope (P less than 0.001) and (TF/P)K/In increased from 14% at the beginning of the IMCD to 25% in the urine. IMCD potassium secretion accounted for about half of the excreted potassium. In the UNPX rats a significant correlation and slope was also obtained (P less than 0.001); (TF/P)K/In at the beginning of IMCD was 24% and increased to 36% in the urine. No difference in slope was noted between the groups. There was a slightly greater absolute potassium secretion after UNPX (0.77 +/- 0.03 S vs. 0.93 +/- 0.04 mueq/min UNPX), but this did not account for most of the difference in potassium excretion noted. We conclude that net potassium secretion occurs along the IMCD in S and UNPX rats. After UNPX, there is significantly greater potassium delivery to the IMCD and a greater kaluresis. The increased kaluresis cannot be accounted for primarily by increased potassium secretion along the IMCD.

Renal medullary plasma flow rate and reabsorption of salt and water from inner medullary collecting duct

1987 ◽  
Vol 65 (12) ◽  
pp. 2415-2421 ◽  
Author(s):  
W. A. Cupples ◽  
H. Sonnenberg
Keyword(s):  
Blood Flow ◽  
Sodium Chloride ◽  
Angiotensin Ii ◽  
Flow Rate ◽  
Plasma Flow ◽  
Collecting Duct ◽  
Urine Osmolality ◽  
Renal Circulation ◽  
Inner Medullary Collecting Duct ◽  
Medullary Collecting Duct

It has been proposed that medullary washout secondary to increased blood flow will limit maximal urine osmolality and reabsorption of salt and water from the inner medullary collecting duct. We have tested this prediction. The function of the inner medullary collecting duct was examined by microcatheterization. Acetylcholine was infused directly into the renal circulation, captopril was infused intravenously, and angiotensin II was infused into the renal circulation in rats which also received captopril. Medullary plasma flow rate, measured by dye–dilution in parallel experiments, was not significantly increased by acetylcholine; it was increased 30% (p < 0.02) by systemic infusion of captopril, and was returned to control by angiotensin II. Acetylcholine increased both urine flow rate and sodium excretion (p < 0.01, p < 0.001, respectively), while captopril increased only sodium excretion (p < 0.025). Angiotensin II blocked the natriuresis due to captopril. None of the treatments altered urine osmolality (p > 0.4 in all cases). Acetylcholine increased the loads of water, sodium, chloride, and total solute delivered to the inner medullary collecting duct. Angiotensin II reduced delivery of water and solutes compared with captopril alone. None of the treatments affected load dependency of reabsorption of water, sodium, chloride, or total solute in the inner medullary collecting duct. We conclude that there is, at most, a weak interaction between medullary blood flow and reabsorption from the inner medullary collecting duct.

Sodium and chloride transport along the inner medullary collecting duct: effect of saline expansion

1980 ◽  
Vol 238 (6) ◽  
pp. F504-F508 ◽  
Author(s):  
H. H. Bengele ◽  
C. Lechene ◽  
E. A. Alexander
Keyword(s):  
Sodium Chloride ◽  
Sodium Transport ◽  
Volume Expansion ◽  
Chloride Transport ◽  
Collecting Duct ◽  
Urine Flow ◽  
Fluid Reabsorption ◽  
Inner Medullary Collecting Duct ◽  
Chloride Excretion ◽  
Medullary Collecting Duct

The effect of volume expansion on inner medullary collecting duct (IMCD) sodium transport remains controversial. Studies employing micropuncture of the IMCD base and tip were interpreted to demonstrate enhanced sodium and chloride reabsorption. Data obtained by microcatheterization evaluating only sodium transport revealed either no reabsorption or net addition. We have examined both sodium and chloride transport by microcatheterization. Volume expansion was comparable to the micropuncture studies: 0.9% saline equal to 10% body wt and then matched to urine flow. The fraction of filtered fluid, sodium, and chloride was analyzed as a function of IMCD length. In eight hydropenic rats 60% of the fluid, 71% of the sodium, and 48% of the chloride delivered to the IMCD was reabsorbed. In six volume-expanded rats no significant net reabsorption of fluid, sodium, or chloride was found. Accordingly, in contrast to the micropuncture results, we have demonstrated that net sodium chloride and fluid reabsorption are absent during volume expansion. We conclude that during volume expansion, fluid, sodium, and chloride excretion increase, in part, because of a reduction in net reabsorption along the IMCD. The degree of volume expansion does not account for the discrepancy between the two techniques.

scholarly journals Effect of amphotericin B on water and urea transport in the inner medullary collecting duct.

1994 ◽  
Vol 5 (1) ◽  
pp. 68-74 ◽  
Author(s):  
Y Yano ◽  
J L Monteiro ◽  
A C Seguro
Keyword(s):  
Hydraulic Conductivity ◽  
Amphotericin B ◽  
Arginine Vasopressin ◽  
Initial Conditions ◽  
Collecting Duct ◽  
Potassium Excretion ◽  
Urea Transport ◽  
Inner Medullary Collecting Duct ◽  
Medullary Collecting Duct

The clinical usefulness of amphotericin B (AMP-B) is limited by its nephrotoxicity, as characterized by decreased RPF, decreased GFR, impaired urinary acidification, and potassium excretion defects. Defects of renal concentrating ability have been noted, but the mechanisms responsible for them have not been investigated. The chief objective of this research was to analyze directly the effect of AMP-B on arginine-vasopressin (AVP)- or dibutyrl cAMP (DcAMP)-stimulated water and urea transport of the inner medullary collecting duct (IMCD) obtained from rats by the in vitro microperfusion technique. AMP-B (10(-5) M) added to the bath fluid in the absence of AVP did not impair the hydraulic conductivity (Lp) and the urea permeability (Pu) of rat IMCD. AMP-B (10(-5) M) added to the bath fluid decreased the AVP-stimulated Lp (x 10(-6) cm/s.atm) of rat IMCD from 19.41 +/- 2.19 to 10.00 +/- 1.39 (P < 0.001), and the reversibility of its action was observed during a third period when Lp increased to 19.80 +/- 2.19 (P < 0.001) after the initial conditions were restored. In addition, AMP-B reduced DcAMP-stimulated Lp from 20.95 +/- 1.75 to 10.52 +/- 0.71 (P < 0.01) in a reversible manner when the drug was withdrawn from the bath. AMP-B also decreased AVP-stimulated Pu (x 10(-5) cm/s) when added to the bath fluid from 36.60 +/- 2.05 to 29.88 +/- 1.36 (P < 0.001), and this effect was reversible after AMP-B was withdrawn from the bath (37.40 +/- 1.36; P < 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Water permeability of apical and basolateral cell membranes of rat inner medullary collecting duct

1990 ◽  
Vol 259 (6) ◽  
pp. F986-F999 ◽  
Author(s):  
B. Flamion ◽  
K. R. Spring
Keyword(s):  
Water Flow ◽  
Water Permeability ◽  
Cell Membranes ◽  
Apical Membrane ◽  
Collecting Duct ◽  
Basolateral Membrane ◽  
Volume Regulatory Decrease ◽  
Water Permeation ◽  
Inner Medullary Collecting Duct ◽  
Medullary Collecting Duct

To quantify the pathways for water permeation through the kidney medulla, knowledge of the water permeability (Posmol) of individual cell membranes in inner medullary collecting duct (IMCD) is required. Therefore IMCD segments from the inner two thirds of inner medulla of Sprague-Dawley rats were perfused in vitro using a setup devised for rapid bath and luminal fluid exchanges (half time, t1/2, of 55 and 41 ms). Differential interference contrast microscopy, coupled to video recording, was used to measure volume and approximate surface areas of single cells. Volume and volume-to-surface area ratio of IMCD cells were strongly correlated with their position along the inner medullary axis. Transmembrane water flow (Jv) was measured in response to a variety of osmotic gradients (delta II) presented on either basolateral or luminal side of the cells. The linear relation between Jv and delta II yielded the cell membrane Posmol, which was then corrected for membrane infoldings. Basolateral membrane Posmol was 126 +/- 3 microns/s. Apical membrane Posmol rose from a basal value of 26 +/- 3 microns/s to 99 +/- 5 microns/s in presence of antidiuretic hormone (ADH). Because of amplification of basolateral membrane, the ADH-stimulated apical membrane remained rate-limiting for transcellular osmotic water flow, and the IMCD cell did not swell significantly. Calculated transcellular Posmol, expressed in terms of smooth luminal surface, was 64 microns/s without ADH and 207 microns/s with ADH. IMCD cells in anisosmotic media displayed almost complete volume regulatory decrease but only partial volume regulatory increase.

scholarly journals Role of the medullary collecting duct in potassium excretion in potassium-adapted animals

1981 ◽  
Vol 20 (5) ◽  
pp. 655-662 ◽  
Author(s):  
Donald A. Schon ◽  
Karen A. Backman ◽  
John P. Hayslett
Keyword(s):  
Collecting Duct ◽  
Potassium Excretion ◽  
Medullary Collecting Duct
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