Osteopontin (OPN) is a secreted phosphoprotein that is constitutively expressed in the normal kidney and is induced by various experimental and pathologic conditions. Several possible functions of OPN have been suggested, however the mechanism and significance of OPN expression are still uncertain. Since high salt concentration or salt crystal have been known to enhance OPN expression in intact kidney or cultured renal cells, in the present study we examined whether or not a low salt condition had an effect on OPN expression in the kidney. Adult male Sprague-Dawley rats were fed either a normal sodium or a sodium deficient diet for 1 week. Kidneys were processed for in situ hybridization using a digoxigenin-labeled riboprobe and for immunohistochemistry using antibodies to OPN, renin, and Na-K-ATPase. In rats fed a normal sodium diet, OPN mRNA and protein were expressed only in the descending thin limbs of Henle's loop (DTL) and in the papillary and pelvic surface epithelium (PSE). In rats fed a sodium deficient diet, there was a marked decrease in OPN immunoreactivity in the DTL, but no changes in PSE. In contrast, no changes were observed in OPN mRNA expression in the DTL by in situ hybridization, indicating that decreased OPN protein expression was a result of translational regulation. As expected, rats fed a sodium deficient diet were associated with increased immunoreactivity for Na-K-ATPase and renin compatible with activation of the renin-angiotensin system. These results suggest that dietary sodium may be involved in the regulation of OPN expression in the DTL of the rat kidney.
Animal ; Diet, Sodium-Restricted* ; Immunohistochemistry ; In Situ Hybridization ; Kidney/metabolism* ; Male ; Na(+)-K(+)-Exchanging ATPase/metabolism ; Rats ; Rats, Sprague-Dawley ; Renin/metabolism ; Sialoglycoproteins/metabolism ; Sialoglycoproteins/antagonists & inhibitors* ; Sodium/deficiency*

Renal Na+, K+-activated adenosinetriphosphatase (Na-K-ATPase) activity and the p-aminohippurate (PAH) transport kinetics were studied in uninephrectomized rats and cold exposed hamsters. In rats, the specific activity of renal Na-K-ATPase increased by approximately 50% in one week after uninephrectomy and remained more or less constant during the next three weeks. The capacity (Jmax) of PAH influx into the renal cortical slice was sharply increased in one week after nephrectomy, but after which it returned to the control level. In cold exposed hamsters, the specific activity of renal Na-K-ATPase did not increase until 48 days of cold exposure at which time it reached approximately 50% above the control level. On the other hand, the Jmax of PAH influx increased by about 80% in 10 days of co1d exposure and somewhat declined thereafter. These results suggest that PAH active transport in the renal slice is not ratelimited by the activity of Na-K-ATPase under physiological conditions.
Aminohippuric Acids/metabolism* ; Animal ; Biological Transport, Active ; Female ; Hamsters ; Hibernation ; Kidney/enzymology* ; Male ; Na(+)-K(+)-Exchanging ATPase/metabolism* ; Nephrectomy ; Rats ; p-Aminohippuric Acid/metabolism*

This study was done to determine the effects of hypothermia on brain cell membrane function and energy metabolism after transient hypoxia-ischemia (HI) in the newborn piglet. Cerebral HI was induced by temporarily complete occlusion of bilateral common carotid arteries with surgical clips and simultaneous breathing with 8% oxygen for 30 min, followed by release of carotid occlusion and normoxic ventilation for 4 hr. Rectal temperature was maintained between 38.0 and 39.0 degrees C in normothermic groups, and between 34.0 and 35.0 degrees C in hypothermic groups for 4 hr after HI. During HI, heart rate, glucose and lactate level in the blood and cerebrospinal fluid increased, and base excess, pH and blood pressure decreased significantly in both normothermic and hypothermic groups. After HI, these abnormalities returned to normal in normothermic group, but lactic acidosis persisted in hypothermic group. Decreased cerebral Na(+),K(+)- ATPase activity and increased lipid peroxidation products, indicative of HI- induced brain injury, were more profound in hypothermic group than in normothermic group. Brain ATP and phosphocreatine levels were not different between normothermic and hypothermic groups. In summary, hypothermia applied immediately after HI for 4 hr did not improve the recovery of brain cell membrane function and energy metabolism in the newborn piglet.
Animal ; Animals, Newborn ; Brain/cytology/*metabolism/physiology ; Cell Membrane/physiology ; Energy Metabolism ; Glucose/metabolism ; *Hypothermia, Induced ; Hypoxia-Ischemia, Brain/*metabolism/physiopathology/therapy ; Lactic Acid/metabolism ; Na(+)-K(+)-Exchanging ATPase/metabolism ; Swine

We sought to know whether a free radical spin trap agent, alpha-phenyl-N-tert-butyl nitrone (PBN) influences brain cell membrane function and energy metabolism during and after transient global hypoxia-ischemia (HI) in the newborn piglets. Cerebral HI was induced by temporary complete occlusion of bilateral common carotid arteries and simultaneous breathing with 8% oxygen for 30 min, followed by release of carotid occlusion and normoxic ventilation for 1 hr (reoxygenationreperfusion, RR). PBN (100 mg/kg) or vehicle was administered intravenously just before the induction of HI or RR. Brain cortex was harvested for the biochemical analyses at the end of HI or RR. The level of conjugated dienes significantly increased and the activity of Na+, K+-ATPase significantly decreased during HI, and they did not recover during RR. The levels of ATP and phosphocreatine (PCr) significantly decreased during HI, and recovered during RR. PBN significantly decreased the level of conjugated dienes both during HI and RR, but did not influence the activity of Na+, K+-ATPase and the levels of ATP and PCr. We demonstrated that PBN effectively reduced brain cell membrane lipid peroxidation, but did not reverse ongoing brain cell membrane dysfunction nor did restore brain cellular energy depletion, in our piglet model of global hypoxic-ischemic brain injury.
Adenosine Triphosphate/metabolism ; Animals ; Animals, Newborn ; *Anoxia ; Brain/*drug effects/metabolism/pathology ; Cell Membrane/*metabolism ; Cerebral Cortex ; *Ischemia ; Lipid Peroxidation ; Na(+)-K(+)-Exchanging ATPase/metabolism ; Neuroprotective Agents/*pharmacology ; Nitrogen Oxides/*pharmacology ; Phosphocreatine/*analogs & derivatives/metabolism ; Reperfusion Injury/*drug therapy ; Support, Non-U.S. Gov't ; Swine ; Time Factors

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

In this study, we tested the hypothesis that decreased cerebral perfusion pressure (CPP) induces cerebral ischemia and worsen brain damage in neonatal bacterial meningitis. Meningitis was induced by intracisternal injection of 10(9) colony forming units of Escherichia coli in 21 newborn piglets. Although CPP decreased significantly at 8 hr after bacterial inoculation, deduced hemoglobin (HbD), measured as an index of changes in cerebral blood flow by near infrared spectroscopy, did not decrease significantly. In correlation analyses, CPP showed significant positive correlation with brain ATP and inverse correlation with brain lactate levels. CPP also correlated positively with HbD and oxidized cytochrome aa3 (Cyt aa3) by near infrared spectroscopy. However, CPP did not show significant correlation with cerebral cortical cell membrane Na+,K+-ATPase activity, nor with levels of lipid peroxidation products. In summary, decreased CPP observed in this study failed to induce cerebral ischemia and further brain injury, indicating that cerebrovascular autoregulation is intact during the early phase of experimental neonatal bacterial meningitis.
Animal ; Animals, Newborn ; Blood Glucose/metabolism ; Cell Membrane/microbiology ; Cell Membrane/enzymology ; Cerebral Cortex/metabolism ; Cerebral Cortex/chemistry ; Cerebral Cortex/blood supply ; Cerebrovascular Circulation/physiology* ; Energy Metabolism/physiology* ; Escherichia coli Infections/physiopathology* ; Escherichia coli Infections/metabolism* ; Glucose/cerebrospinal fluid ; Glucose/analysis ; Intracranial Pressure ; Lactic Acid/cerebrospinal fluid ; Lactic Acid/blood ; Lactic Acid/analysis ; Lipid Peroxidation/physiology ; Meningitis, Bacterial/physiopathology* ; Meningitis, Bacterial/metabolism* ; Na(+)-K(+)-Exchanging ATPase/metabolism ; Spectroscopy, Near-Infrared ; Swine