The effect of antidiuretic hormone on solute flows in mammalian collecting tubules

167

AB STRA CT Electrical and permeability features of the distal convoluted tubule (DCT) and the cortical collecting tubule (CCT) were examined using the technique in which isolated segments of rabbit tubules were perfused in vitro. When rabbits were given a regular diet and tubules were perfused and bathed in artificial solutions simulating plasma ultrafiltrate, the potential difference (PD) was + 3.7+1.9 mV in the CCT and -40.4±2.8 mV in the DCT. When rabbits were given a low sodium, high potassium diet plus i.m. deoxycorticosterone acetate (DOCA) (1 mg/kg per day), the PD in both the CCT (-30.8±3.9 mV) and the DCT (-33.8±5.5 mV) was negative. The PD in the CCT was quantitatively similar to that of diet plus DOCA when animals were given DOCA alone. The PD in both segments was inhibited by ouabain (10' M) in the bath or by amiloride (10' M) in the perfusate. Addition of vasopressin (200 AU/ml) to the bath caused a gradual decline of PD to zero in the CCT but failed to produce a potential response in the DCT. Osmotic water permeability was essentially zero in both segments in the absence of vasopressin. After addition of the vasopressin to the bath, osmotic water permeability in the DCT remained zero but increased to 71.9+25.5 x 10-7 cm/s per atm in the CCT. We conclude that both segments are similar in that each possesses an electrogenic transport process but that these segments differ in that: (a) the CCT requires either exogenous or endogenous mineralocorticoid to maintain a maximal negative PD, whereas the PD in the DCT appears to be independent of mineralocorticoid effect; and (b) the CCT responds to vasopressin with a marked rise in water permeability, whereas the DCT is impermeable to water before and after addition of vasopressin.Dr. Imai's present address is the Department of Pharmacology, Jichi Medical School, Tochigi, Japan 329-04.

Section: Methodssupporting

confidence: 90%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

A functional comparison of the cortical collecting tubule and the distal convoluted tubule.

Gross¹,

Imai²,

Kokko³

1975

167

“…These experiments were performed either without antidiuretic hormone (ADH) in the bath or with either 0.2 or 2.0 mU ml1 ADH. These results are summarized in Table II and indicate that the tALH is as impermeable to diffusional water flow as is the cortical and outer medullary collecting duct in the absence of ADH (13,14). After addition of 0.2 mU m1l-ADH The calculated passive permeability coefficient for chloride, Pci, was extremely high.…”

Section: Methodsmentioning

confidence: 95%

Sodium chloride, urea, and water transport in the thin ascending limb of Henle. Generation of osmotic gradients by passive diffusion of solutes.

Imai¹,

Kokko²

1974

187

A B S T R A C T Studies were designed to examine whether the thin ascending limb of Henle (tALH) decreases its luminal solute concentration by an active or a passive transport process. In all experiments isolated segments of rabbit tALH were perfused in vitro. \Vhen tubules were perfused with solutions identical to the bath, active transport of NaCI was excluded by the following: (a) osmolality of the collected fluid remained unchanged and the same as the bath, (b) net water reabsorption could not be demonstrated, and (c) transtubular potential difference was zero. Isotopic permeability coefficients (X 10' cm sol) were calculated from the disappearance rate of the respective isotope added to the perfusate. These values indicate that tALH is moderately permeable to [14Clurea (6.97±1.95) while hiving a higher permeability to 'Na (25.5±1.8) and 'Cl (117+ 9.1) than any other segment similarly studied. The influx (bath-to-lumen) isotopic permeabilities were not statistically different from the above efflux permeahilities. Osmotic water permeability was immeasurably small. When tALH were perfused with a 600 mosmol/liter solution predominantly of NaCl against a 600 mosmol/ liter bath in which 50% of osmolality was NaCl and 50% urea (to simulate in vivo papillary interstitium), the collected fluid osmolality was decreased significantly below that of the bath (300 mosmol/liter/mm of tubule).The decrease in osmolality was due to greater efflux of

“…The osmolality at the collecting end could then be calculated as the product of the osmolality of the perfusion solution by the concentration index of the volume marker in the collected fluid (15). The mean transtubular osmotic gradient was calculated as the logarithmic mean (16,17) of the osmotic gradient at the perfusing and collecting end.…”

Section: Introductionmentioning

confidence: 99%

Effects of Ethacrynic Acid on the Isolated Collecting Tubule

Abramow¹

1974

A B STRACT Effects of the diuretic ethacrynic acid on osmotic water permeability were investigated in the isolated perfused collecting tubule of the rabbit kidney.The base-line water permeability of the collecting tubule was not affected when the drug (10-'M) alone was added to the bathing medium. Vasopressin alone in the bathing medium (2, 5 AU/ml) elicited a significant increase in osmotic water absorption. With vasopressin kept in the bathing medium, the addition of 10-'M ethacrynic acid depressed the hydro-osmotic effect of vasopressin by 50%. This inhibitory effect of low concentrations of ethacrynic acid could be surmounted by high, supramaximal dosage levels of vasopressin.When 10-4M ethacrynic acid was added to the bathing medium before vasopressin, the hydro-osmotic effect of vasopressin and the diuretic in combination was insignificant.Dibutyryl adenosine 3'5'-monophosphate (10-4-10-'M) alone in the bathing medium significantly increased baseline osmotic water flow, mimicing the effect of antidiuretic hormone. When ethacrynic acid was added together with the nucleotide, the permeability remained at the same high level. Theophylline, like the nucleotide and vasopressin, produced a significant hydro-osmotic effect. The magnitude of this responise was not affected by further addition of ethacrynic acid (10-4`\).It was concluded that ethacrynic acid is an antagonist of antidiuretic hormone. The antagonism probably occurs at the level of the receptor site of the hormone on the peritubular membrane. Antagonism to circulating antidiuretic hormone may therefore be one of the factors involved in the loss of renal concentrating ability brought about by ethacrynic acid diuresis.