Effect of antidiuretic hormone on water and solute permeation, and the activation energies for these processes, in mammalian cortical collecting tubules

164

A B S T R A C T Medullary thick ascending limbs ofHenle's loop of the Swiss-Webster mouse were perfused in vitro with an isotonic perfusate and a Ringer's bathing medium. In five studies, addition of a supramaximal concentration of synthetic arginine vasopressin (AVP) to the bathing medium resulted in an increase in electrical potential difference (PD) from 5.0±1.5 mV, lumen positive, to 10.7±1.4 mV (P < 0.001). When AVP was removed, the PD returned to 2.6±0.9 mV (P < 0.001), then increased again to 6.9±1.7 mV (P < 0.01) when AVP was added a second time. A significant, but submaximal, increase in PD of 2.3±0.6 mV (P < 0.05) was observed in five medullary thick ascending limbs when AVP was added to the bathing medium at a concentration of 10 AU/ml. This increase was approximately one-third of the response observed at a concentration of 100 ,uU/ml in the same tubule. No further increment in PD was observed in five medullary thick ascending limbs when the AVP concentration was increased from 100 to 1,000 ,uU/ml. In seven thick ascending limbs, the effect of AVP on PD was reproduced by the addition of 8-[p-chlorophenylthio]-cyclic 3',5'-adenosine monophosphate to the bathing medium at a final concentration of 0.1 mM. AVP increased unidirectional chloride flux from lumen to bath from 29.3±3.2 to 69.8±6.2 peq/cm per s (P < 0.01) in spite of an increase in the lumen positive PD from 1.6±0.5 mV to 7.0+0.6 mV (P < 0.001). Unidirectional chloride flux from bath to lumen was not affected by AVP. In another series of experiments, net chloride flux increased from 15.6±3.0 to 41.7±5.3 peq/cm per s (P < 0.05) after addition of AVP. The effect of AVP on hydraulic water pertneability (Lp) was examined by adding raffinose to the bathing medium in both the

Section: Discussionmentioning

confidence: 96%

Section: Methodsmentioning

confidence: 99%

Effect of vasopressin on electrical potential difference and chloride transport in mouse medullary thick ascending limb of Henle's loop.

Hall¹,

Varney²

1980

164

“…Fluid flux (J v ) was calculated as: J v ϭ V o Ϫ V l . P f was calculated using the equation of AlZahid et al (18) as described (14).…”

Section: Methodsmentioning

confidence: 99%

Changes in aquaporin-2 protein contribute to the urine concentrating defect in rats fed a low-protein diet.

Sands¹,

Naruse²,

Jacobs³

et al. 1996

Low-protein diets cause a urinary concentrating defect in rats and humans. Previously, we showed that feeding rats a low (8%) protein diet induces a change in urea transport in initial inner medullary collecting ducts (IMCDs) which could contribute to the concentrating defect. Now, we test whether decreased osmotic water permeability (P f ) contributes to the concentrating defect by measuring P f in perfused initial and terminal IMCDs from rats fed 18 or 8% protein for 2 wk. In terminal IMCDs, arginine vasopressin (AVP)-stimulated osmotic water permeability was significantly reduced in rats fed 8% protein compared to rats fed 18% protein.

“…In response to vasopressin, concentrated urine is produced by water reabsorption across the kidney collecting duct. Water is thought to pass through water-permeable pores, i.e., "water channels," in the apical membrane of this nephron segment (2)(3)(4)(5)(6)(7). We recently cloned a cDNA of the apical collecting duct water channel of the rat kidney (8), based on the conserved amino acid sequence in the members of the major intrinsic protein (MIP) l (9) family, including channel integrate protein of 28 kD (CHIP28), a water channel of red blood cells, and renal proximal and descending tubules (10)(11)(12).…”

Section: Introductionmentioning

confidence: 99%

Cloning, characterization, and chromosomal mapping of human aquaporin of collecting duct.

Sasaki¹,

Fushimi²,

Saito³

et al. 1994

206