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Na,K-ATPase activity in renal tubule cells from Milan hypertensive rats
M L Melzi1, A Bertorello, Y Fukuda
1Department of Pediatrics, St. Göran's Children's Hospital, Karolinska Institute, Stockholm, Sweden.
Abstract:
Several abnormalities of cation transport have been described in the Milan hypertensive rats (MHS). In this study we examined Na,K-ATPase activity in proximal convoluted tubules (PCT) cells and medullary thick ascending limb of Henle cells (TAL) from MHS and from the Milan normotensive rats (MNS). Na,K-ATPase activity was determined as 32P-ATP hydrolysis in single tubule segments. Na,K-ATPase activity (pmol Pi/mm t/h) was significantly higher in MHS than MNS both in PCT (903 +/- 227 n = 8 v 506 +/- 285 n = 12) and TAL (4324 +/- 800 n = 5 v 3063 +/- 625 n = 5). Na,K-ATPase dependent respiration was determined in PCT cell from MNS and MHS. Under basal condition Na,K-ATPase dependent respiration (mumol O2/mg protein/h) was higher in MHS than in MNS (24.2 +/- 1.8 n = 5 v 16.1 +/- 0.4 n = 5). When the cells were Na loaded by amphotericin Na,K-ATPase dependent respiration increased significantly more in MHS than MNS (38.4 +/- 1.6 v 26.8 +/- 2.2 n = 4). Thus, Na,K-ATPase activity is higher in renal tubule cells both at normal intracellular Na and after the cells have been Na loaded. The results indicate that regulation of Na homeostasis in renal tubule cell is different in MHS and MNS.
Insights
Milan hypertensive rats exhibit higher sodium-potassium adenosine triphosphatase (Na,K-ATPase) activity in kidney tubule cells compared to normotensive rats. This suggests altered sodium homeostasis regulation in hypertension.
Area of Science:
- Nephrology
- Physiology
- Biochemistry
Background:
- Cation transport abnormalities are noted in Milan hypertensive rats (MHS).
- Understanding sodium-potassium adenosine triphosphatase (Na,K-ATPase) function is crucial for renal physiology.
Purpose of the Study:
- To investigate Na,K-ATPase activity in proximal convoluted tubule (PCT) and medullary thick ascending limb of Henle (TAL) cells.
- To compare Na,K-ATPase activity and dependent respiration between MHS and Milan normotensive rats (MNS).
Main Methods:
- Measured Na,K-ATPase activity via 32P-ATP hydrolysis in single tubule segments.
- Assessed Na,K-ATPase dependent respiration in PCT cells under basal and sodium-loaded conditions.
Main Results:
- Significantly higher Na,K-ATPase activity was observed in both PCT and TAL cells of MHS compared to MNS.
- Na,K-ATPase dependent respiration was elevated in MHS PCT cells, both basally and after sodium loading.
- Increased Na,K-ATPase activity in MHS suggests altered sodium regulation in renal tubule cells.
Conclusions:
- Na,K-ATPase activity is upregulated in renal tubule cells of Milan hypertensive rats.
- These findings indicate a distinct regulation of sodium homeostasis in the kidneys of MHS.
- This difference in Na,K-ATPase function may contribute to the hypertensive phenotype.