Journal article
Maturation of proximal tubule Na+/H+ antiporter activity in sheep during transition from fetus to newborn
American journal of physiology. Renal physiology, Vol.267(4), pp.F537-F545
10/01/1994
DOI: 10.1152/ajprenal.1994.267.4.F537
PMID: 7943353
Abstract
We have studied maturational changes in the kinetics of the proximal tubule Na+/H+ antiporter. Microvillus membrane vesicles were prepared from renal cortex of fetal and newborn lambs. Amiloride-sensitive uptake of 22Na+ by these vesicles was measured and Woolf-Augustinsson-Hofstee plots were used to determine the Michaelis constant (Km) and rate of maximal uptake (Vmax). Initial studies of fetal lambs at 130-132 days gestation (n = 5; term is 145 days) and 3- to 4-day-old lambs (n = 5) revealed no maturational change in Km (7.27 +/- 1.25 for fetuses and 9.01 +/- 1.03 mM for lambs); however, there was a 242% increase in Vmax (from 1.28 +/- 0.33 in the fetuses to 4.37 +/- 0.85 nmol.s-1.mg protein-1 in the lambs, P = 0.005). Further definition of the developmental change in Na+/H+ antiporter Vmax was obtained when 144-day-gestation fetuses (n = 5) were compared with 24-h-old sibling lambs (n = 5) that had been delivered by cesarean section at 144 days gestation. Again, no significant difference was seen in Na+/H+ antiporter Km (14.9 +/- 6.5 for fetuses and 12.5 +/- 3.4 mM for lambs); however, a significant increase in Na+/H+ antiporter Vmax occurred (from 1.41 +/- 0.51 in the fetuses to 3.32 +/- 0.37 nmol.s-1.mg protein-1 in the lambs, P < 0.01). This study shows that there is a maturational increase in renal cortical Na+/H+ antiporter Vmax during the transition from fetal to newborn life. This increase parallels the increase in renal tubular Na+ reabsorption that occurs at this time.
Details
- Title: Subtitle
- Maturation of proximal tubule Na+/H+ antiporter activity in sheep during transition from fetus to newborn
- Creators
- Edward N Guillery - Department of Pediatrics, University of Iowa, Iowa CityLawrence P Karniski - Department of Pediatrics, University of Iowa, Iowa CityMichael S Mathews - University of IowaJean E Robillard - Department of Pediatrics, University of Iowa, Iowa City
- Resource Type
- Journal article
- Publication Details
- American journal of physiology. Renal physiology, Vol.267(4), pp.F537-F545
- DOI
- 10.1152/ajprenal.1994.267.4.F537
- PMID
- 7943353
- ISSN
- 1931-857X
- eISSN
- 1522-1466
- Language
- English
- Date published
- 10/01/1994
- Academic Unit
- Molecular Physiology and Biophysics; Nephrology, Dialysis and Transplantation; Stead Family Department of Pediatrics; Nephrology; Medicine Administration; Internal Medicine
- Record Identifier
- 9984025408402771
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