Effect of amiloride on the renal response to saline expansion in new‐born dogs.

Banks, Robert O.; Kleinman, Leonard I.

doi:10.1113/jphysiol.1978.sp012205

Cited by 11 publications

(6 citation statements)

References 14 publications

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“…The Kt, for potassium in cortex was 2.3 f 0.09 urinary potassium excretion (1,34) confirm that amiloride aland 2.2 f 0.07 mM in potassium-supplemented and control animals, respectively. These differences were not statistically significant.…”

Section: Mean (Sem)supporting

confidence: 49%

“…Moreover, there was no and not the discontinuation of the high potassium infusion. The difference in amiloride-sensitive potassium secretion between data supporting these assumptions have been previously reviewed (1,34) and support the assertion that this method provides a control and potassium-supplemented animals. Even if the two reasonable estimate of amiloride-sensitive potassium secretion.…”

Section: Mean (Sem)mentioning

confidence: 59%

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The Role of Cortical Na,K-ATPase in Distal Nephron Potassium Secretion by the Immature Canine Kidney

1991

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ABSTRACT. Amiloride-sensitive potassium secretion in response to acute potassium loading is lower in the newborn than in the adult. Potassium secretion is a function of late distal tubule and cortical collecting tubule Na,K-ATPase activity. Na,K-ATPase activity in vivo is determined by enzyme abundance and catalytic turnover. Chronic potassium supplementation increases potassium secretory capacity in the adult by increasing enzyme abundance in the late distal and cortical collecting tubules. We hypothesized that the lower potassium secretory capacity of the newborn was the result of lower late distal and cortical collecting tubule Na,K-ATPase activity and could be similarly enhanced. To test this hypothesis, newborn dogs were supplemented with 6 mmol KC1.d-'. kg-' for 1 wk; agematched litter mate controls were not ( n = 8 pairs). Potassium supplementation resulted in a mean increase in V,,, Na,K-ATPase activity in vitro (proportional to pump abundance) of 70 + 42%. Mean Na,K-ATPase activities + S E M were 279 + 58 versus 198 2 44 nmol inorganic P.h-I-gg DNA-', p = 0.05. However, amiloride-sensitive potassium secretion after an acute potassium load of 20 pmol. min-'. kg-' over 150 min was not enhanced (9.6 +-1.8 versus 8.9 + 0.8 pmol . min-' .kg-', potassium-supplemented versus control animals). We conclude that lower enzyme abundance is not primarily responsible for the newborn's lower potassium secretory capacity. W e speculate that the factor that limits secretion in the newborn during acute potassium loading does so by restricting catalytic turnover of the enzyme in vivo. (Pediatr Res 30: 457-463,1991) Abbreviations KIl2, substrate concentration at which the reaction velocity is half maximum Na,K-ATPase, sodium-potassium-activated adenosine triphosphatase T ' H~~, free water reabsorption TFK, tubular fluid potassium concentration TTKG, transtubular potassium gradient is less than that of the mature nephron (1). Transtubular potassium secretion in these nephron segments is driven by basolateral membrane Na,K-ATPase (2, 3). Na,K-ATPase activity has been shown to be lower in neonatal than adult nephron segments (4-6). It is possible, therefore, that the potassium secretory response of the immature nephron may be limited by lower Na,K-ATPase activity.Results of a study that examined the effect of increasing Na,KATPase activity on the renal response to acute potassium loading in newborn dogs did not support this possibility (7). In that study, newborn dogs were subjected to chronic potassium supplementation for 1 to 3 wk after birth to enhance Na,K-ATPase activity in potassium secretory nephron segment(s). Chronic potassium supplementation doubled V,,, cortical Na,K-ATPase activity compared with controls (who received distilled water supplementation), but did not enhance urinary excretion of an acute potassium load in the newborn dog. These results were interpreted to indicate that Na,K-ATPase pump abundance is not rate limiting in excretion of a potassium load in the newborn. However, it is possible that wate...

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Section: Mean (Sem)supporting

confidence: 49%

Section: Mean (Sem)mentioning

confidence: 59%

The Role of Cortical Na,K-ATPase in Distal Nephron Potassium Secretion by the Immature Canine Kidney

1991

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“…However, continued isotonic reabsorption during distal blockade is not excluded by these ratios. The dose of amiloride used in this study abolishes nearly all potassium secretion (17,(26)(27)(28) and inhibits bicarbonate reabsorption in the collecting tubule (29,30). Moreover, proximal fractional bicarbonate reabsorption in protocol I under control conditions in the adult dog (95.6%) was very close to the FRHC03 of 94% before the distal tubule in hydropenic dogs by micropuncture (3 1).…”

Section: Discussionmentioning

confidence: 85%

Effects of Euvolemic and Hypervolemic Hyperbicarbonemia on Segmental Nephron HCO3 Reabsorption in the Newborn Dog1

Lorenz

1990

Pediatr Res

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ABSTRACT. Studies were undertaken to determine the effect of elevated plasma bicarbonate concentration (PHC03) with and without volume expansion on segmental nephron H C 0 3 reabsorption in newborn and adult dogs using the technique of distal blockade. Reabsorption of bicarbonate per mL glomerular filtrate (RHC03lGFR) in the proximal nephron was more suppressed in euvolemic newborns than euvolemic adults as PHC03 was increased from baseline to 50-70 mM. Inasmuch as total nephron reabsorption has been shown to be essentially complete under these conditions in both newborns and adults, distal nephron H C 0 3 delivery and the fraction of the distal H C 0 3 load reabsorbed must have been greater in euvolemic newborns than adults when P H C 0 3 was elevated. Total nephron RHC03/GFR was less suppressed by NaHC03 volume expansion in the newborn than it was in the adult. However, proximal nephron RHC03/GFR was similarly suppressed by NaHC03 volume expansion in newborns and adults. Thus, the NaHC03-expanded newborn must have reabsorbed a greater proportion of the increased distal HC03 load than did the NaHC03-expanded adult. Proximal nephron H C 0 3 reabsorption is a balance between reabsorption effected by active proton secretion and passive H C 0 3 back leak. Euvolemic increase in peritubular HCO3 concentration has been shown to suppress proximal tubular proton secretion; volume expansion increases proximal tubule H C 0 3 permeability and back leak. Thus, we interpret these results to indicate that: 1 ) the limited capacity of the immature proximal tubule for proton secretion is most likely responsible for the greater suppression of proximal RHC03/GFR by increased PHC03 in euvolemic newborn dogs compared with adults; 2) the increase in H C 0 3 permeability of the immature proximal nephron with volume expansion is no greater than that which occurs in the mature proximal nephron with volume expansion; and 3) the immature distal nephron displays a greater propensity for HCO3 reabsorption as PHC03 is increased than does the mature distal nephron, with or without volume expansion. (Pediatv Res 27: 604-611, 1990) Abbreviations FRHC03, fractional reabsorption of the filtered bicarbonate load GFR, glomerular filtration rate PHC03, plasma bicarbonate concentration

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“…On the other hand, newborn puppies appear to be more sensitive to amiloride than were adults (2). Under steady state conditions, amiloride increased fractional sodium excretion in puppies to 3.8% while that of adult dogs increased to only 2.5%.…”

mentioning

confidence: 92%

“…Under steady state conditions, amiloride increased fractional sodium excretion in puppies to 3.8% while that of adult dogs increased to only 2.5%. These observations led Banks and Kleinman (2) to conclude that proximal tubular function in newborn puppies is similar to that of adults but that the distal tubule is not fully mature.…”

mentioning

confidence: 99%

Effect of Acetazolamide on Renal Function of the Newborn Piglet

Noordewier¹,

Bailie²,

Hook³

1981

Dev Pharmacol Ther

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The effects of renal development on the response of newborns to acetazolamide were determined in an animal model, 5- and 20-day-old piglets. Increasing doses of acetazolamide increased both sodium and potassium excretion in 5-day-old piglets. Sodium excretion increased from 1.89 μEq/min during control periods to 15.7 μEq/min during infusion of acetazolamide (75 mg/kg/h). Potassium excretion increased to 20 μEq/min during acetazolamide infusion and urine pH increased from 5.7 to over 8.0. Sodium excretion by 20-day-old piglets given acetazolamide was similar to that of 5-day-old piglets but potassium excretion was twice as great (40 μEq/min). Changes in urine pH of the two groups were identical. It is concluded that the natriuretic response of 5-day-old piglets to acetazolamide is similar to that of older animals. In newborn piglets, moderate increases in sodium excretion by acetazolamide were accompanied by a marked kaliuresis. These data may identify a role for carbonic anhydrase in potassium excretion by newborns similar to that of adults.

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Effect of amiloride on the renal response to saline expansion in new‐born dogs.

Cited by 11 publications

References 14 publications

The Role of Cortical Na,K-ATPase in Distal Nephron Potassium Secretion by the Immature Canine Kidney

The Role of Cortical Na,K-ATPase in Distal Nephron Potassium Secretion by the Immature Canine Kidney

Effects of Euvolemic and Hypervolemic Hyperbicarbonemia on Segmental Nephron HCO3 Reabsorption in the Newborn Dog1

Effect of Acetazolamide on Renal Function of the Newborn Piglet

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