Biomaterial Database

Maturation of proximal tubule Na+/H+ antiporter activity in sheep during transition from fetus to newborn. 1994

E N Guillery, and L P Karniski, and M S Mathews, and J E Robillard

Department of Pediatrics, University of Iowa, Iowa City.

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.

UI	MeSH Term	Description	Entries
D007672	Kidney Cortex	The outer zone of the KIDNEY, beneath the capsule, consisting of KIDNEY GLOMERULUS; KIDNEY TUBULES, DISTAL; and KIDNEY TUBULES, PROXIMAL.	Cortex, Kidney
D007687	Kidney Tubules, Proximal	The renal tubule portion that extends from the BOWMAN CAPSULE in the KIDNEY CORTEX into the KIDNEY MEDULLA. The proximal tubule consists of a convoluted proximal segment in the cortex, and a distal straight segment descending into the medulla where it forms the U-shaped LOOP OF HENLE.	Proximal Kidney Tubule,Proximal Renal Tubule,Kidney Tubule, Proximal,Proximal Kidney Tubules,Proximal Renal Tubules,Renal Tubule, Proximal,Renal Tubules, Proximal,Tubule, Proximal Kidney,Tubule, Proximal Renal,Tubules, Proximal Kidney,Tubules, Proximal Renal
D007700	Kinetics	The rate dynamics in chemical or physical systems.
D008871	Microvilli	Minute projections of cell membranes which greatly increase the surface area of the cell.	Brush Border,Striated Border,Border, Brush,Border, Striated,Borders, Brush,Borders, Striated,Brush Borders,Microvillus,Striated Borders
D008985	Monensin	An antiprotozoal agent produced by Streptomyces cinnamonensis. It exerts its effect during the development of first-generation trophozoites into first-generation schizonts within the intestinal epithelial cells. It does not interfere with hosts' development of acquired immunity to the majority of coccidial species. Monensin is a sodium and proton selective ionophore and is widely used as such in biochemical studies.	Coban,Monensin Monosodium Salt,Monensin Sodium,Monensin-A-Sodium Complex,Rumensin,Monensin A Sodium Complex
D002462	Cell Membrane	The lipid- and protein-containing, selectively permeable membrane that surrounds the cytoplasm in prokaryotic and eukaryotic cells.	Plasma Membrane,Cytoplasmic Membrane,Cell Membranes,Cytoplasmic Membranes,Membrane, Cell,Membrane, Cytoplasmic,Membrane, Plasma,Membranes, Cell,Membranes, Cytoplasmic,Membranes, Plasma,Plasma Membranes
D005333	Fetus	The unborn young of a viviparous mammal, in the postembryonic period, after the major structures have been outlined. In humans, the unborn young from the end of the eighth week after CONCEPTION until BIRTH, as distinguished from the earlier EMBRYO, MAMMALIAN.	Fetal Structures,Fetal Tissue,Fetuses,Mummified Fetus,Retained Fetus,Fetal Structure,Fetal Tissues,Fetus, Mummified,Fetus, Retained,Structure, Fetal,Structures, Fetal,Tissue, Fetal,Tissues, Fetal
D005865	Gestational Age	The age of the conceptus, beginning from the time of FERTILIZATION. In clinical obstetrics, the gestational age is often estimated from the onset of the last MENSTRUATION which is about 2 weeks before OVULATION and fertilization. It is also estimated to begin from fertilization, estrus, coitus, or artificial insemination.	Embryologic Age,Fetal Maturity, Chronologic,Chronologic Fetal Maturity,Fetal Age,Maturity, Chronologic Fetal,Age, Embryologic,Age, Fetal,Age, Gestational,Ages, Embryologic,Ages, Fetal,Ages, Gestational,Embryologic Ages,Fetal Ages,Gestational Ages
D000584	Amiloride	A pyrazine compound inhibiting SODIUM reabsorption through SODIUM CHANNELS in renal EPITHELIAL CELLS. This inhibition creates a negative potential in the luminal membranes of principal cells, located in the distal convoluted tubule and collecting duct. Negative potential reduces secretion of potassium and hydrogen ions. Amiloride is used in conjunction with DIURETICS to spare POTASSIUM loss. (From Gilman et al., Goodman and Gilman's The Pharmacological Basis of Therapeutics, 9th ed, p705)	Amidal,Amiduret Trom,Amiloberag,Amiloride Hydrochloride,Amiloride Hydrochloride, Anhydrous,Kaluril,Midamor,Midoride,Modamide,Anhydrous Amiloride Hydrochloride,Hydrochloride, Amiloride,Hydrochloride, Anhydrous Amiloride,Trom, Amiduret
D000818	Animals	Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA.	Animal,Metazoa,Animalia