The present study was done to determine whether endogenous nitric oxide (NO) plays a role in the regulation of sodium transporters in the kidney. Male Sprague-Dawley rats were treated with NG-nitro-L-arginine methyl ester (L-NAME, 100 mg/L drinking water) for 4 weeks. Control rats were supplied with tap water without drugs. Expression of Na, K-ATPase, type 3 Na/H exchanger (NHE3), Na/K/2Cl cotransporter (BSC1), and thiazide-sensitive Na/Cl cotransporter (TSC) proteins was determined in the kidney by Western blot analysis. Catalytic activity of Na,K-ATPase was also determined. The treatment with L-NAME significantly and steadily increased the systemic blood pressure. Total and fractional excretion of urinary sodium decreased significantly, while creatinine clearance remained unaltered. Neither plasma renin activity nor aldosterone concentration was significantly altered. The alpha1 subunit expression and the catalytic activity of Na, K-ATPase were increased in the kidney. The expression of NHE3, BSC1 and TSC was also increased significantly. These results suggest that endogenously-derived NO exerts a tonic inhibitory effect on the expression of sodium transporters, including Na, K-ATPase, NHE3, BSC1, and TSC, in the kidney.
Animals ; Blotting, Western ; Carrier Proteins/*biosynthesis ; Enzyme Inhibitors/pharmacology ; Kidney/drug effects/metabolism ; Male ; NG-Nitroarginine Methyl Ester/*pharmacology ; Na(+)-K(+)-Exchanging ATPase/biosynthesis ; Nitric Oxide Synthase/*antagonists & inhibitors/metabolism ; Rats ; Rats, Sprague-Dawley ; Receptors, Drug/biosynthesis ; Sodium/*metabolism ; Sodium Chloride Symporters/biosynthesis ; Sodium-Hydrogen Antiporter/biosynthesis ; Sodium-Potassium-Chloride Symporters/biosynthesis

PURPOSE: To evaluate the expression of the Na(+)-K(+)-2Cl(-)-cotransporter 2 (NKCC2) in the ischemic rat retina. METHODS: Retinal ischemia was induced by pressures 90 to 120 mmHg, above systemic systolic pressure. Immunohistochemistry and western blot analysis were performed. RESULTS: NKCC2 is expressed in the normal retina and its expression is increased by ischemia caused by intraocular pressure elevation. NKCC2 immunoreactivity was observed mainly in axon bundles of ganglion cells and horizontal cell processes in the retina. NKCC2 expression continuously increased with a peak value 3 days (to 415% of normal levels) after ischemic injury, and then gradually decreased to 314% of controls until 2 weeks post injury. The mean density of NKCC2-labeled ganglion cells per mm2 changed from 1,255 +/- 109 in normal retinas to 391 +/- 49 and 185 +/- 37 at 3 days and 2 weeks after ischemia, respectively (p < 0.05), implying cell death of ganglion cells labeled with NKCC2. CONCLUSIONS: Taken together, these results suggest that NKCC2, which is expressed in retinal ganglion and horizontal cells, may contribute to cell death by ischemic injury in the retina, although the molecular mechanisms involved remain to be clarified.
Animals ; Blotting, Western ; Disease Models, Animal ; Immunohistochemistry ; Intraocular Pressure ; Ischemia/etiology/*metabolism ; Male ; Microscopy, Confocal ; Ocular Hypertension/*complications/metabolism/physiopathology ; Rats ; Rats, Sprague-Dawley ; Retinal Diseases/etiology/*metabolism ; Retinal Ganglion Cells/*metabolism/pathology ; Sodium-Potassium-Chloride Symporters/*biosynthesis

TRPV5 is believed to play an important role in the regulation of urinary calcium excretion. We assessed the effects of hydrochlorothiazide (HCTZ) on the expression of TRPV5, calbindin-D28K, and several sodium transporters in hypercalciuric rats. Sprague- Dawley rats were divided into 4 groups; control, HCTZ, high salt, and high salt with HCTZ group in experiment 1; control, HCTZ, high calcium (Ca), and high Ca with HCTZ group in experiment 2. To quantitate the expression of TRPV5, calbindin- D28K, and sodium transporters, western blotting was performed. In both experiments, HCTZ significantly decreased urinary calcium excretion. TRPV5 protein abundance decreased in all hypercalciuric rats, and restored by HCTZ in both high salt with HCTZ and high Ca with HCTZ group. Calbindin-D28K protein abundance increased in the high salt and high salt with HCTZ groups, but did not differ among groups in experiment 2. Protein abundance of NHE3 and NKCC2 decreased in all hypercalciuric rats, and were restored by HCTZ in only high Ca-induced hypercalciuric rats. In summary, protein abundance of TRPV5, NHE3, and NKCC2 decreased in all hypercalciuric rats. The hypocalciuric effect of HCTZ is associated with increased protein abundance of TRPV5 in high salt or calcium diet-induced hypercalciuric rats.
Animals ; Biological Transport ; Calcium/urine ; Calcium Channels/chemistry ; Calcium-Binding Protein, Vitamin D-Dependent/*biosynthesis ; Hydrochlorothiazide/pharmacology ; Hypercalciuria/*therapy ; Male ; Models, Biological ; Rats ; Rats, Sprague-Dawley ; Sodium/*metabolism ; Sodium-Hydrogen Antiporter/chemistry ; Sodium-Potassium-Chloride Symporters/metabolism ; TRPV Cation Channels/*biosynthesis/chemistry ; Thiazides/*pharmacology