Abstract

Introduction

Materials & Methods

Results

Discussion & Conclusion

References

Discussion
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Animal Protocol
Male Dahl salt-sensitive (Dahl-S) and salt-resistant (Dahl-R) rats at 6 weeks of age were maintained on a diet of standard rat chow (0.3% NaCl) and water ad libitum for a one week observation period. The rats were then divided into 6 different diet groups as follows: Dahl-R, 0.3% NaCl control diet; Dahl-R, 6.0% NaCl enriched diet; Dahl-R, 6.0% NaCl + 0.07% tungsten enriched diet ; Dahl-S, 0.3% NaCl control diet ; Dahl-S, 6.0% NaCl enriched diet ; and Dahl-S, 6.0% NaCl + 0.07% tungsten enriched diet. All rats were maintained on either the 0.3% NaCl, the 6.0% NaCl diet or the 6.0% NaCl + 0.07% tungsten diet (ICN Nutritional Biochemicals; Cleveland, OH) for 4 weeks. Mature SHR and WKY rats were fed with a tungsten enriched (sodium tungstate: 0.7 g/kg), molybdenum depleted diet and water ad libitum.

A femoral catheter was inserted for blood pressure measurements using 4% xylocaine as a local anesthetic. After allowing the animals to recover from the surgical procedure, mean, systolic and diastolic blood pressure was continuously monitored in conscious, free roaming animals via a transducer for 30 minutes.

In order to assess tungsten’s inhibitory effect in the different rat strains, samples of the spinotrapezius muscle or mesentery from each animal were collected and assayed for xanthine oxidase activity (see Parks et al. 1988, Conversion of xanthine dehydrogenase to oxidase in ischemic rat intestine: a reevaluation. Am J Physiol :G768-74).

The rats were anesthetized by intravenous injection of 50 mg/kg body weight sodium pentobarbital and the ileocecal portion of the mesentery was gently exteriorized for intravital microscopy. The preparation was kept at 37°C and continuously superfused with a Krebs-Henseleit bicarbonate-buffered solution saturated with a 95% nitrogen - 5% carbon dioxide gas mixture. Special precautions were taken to avoid interruption of the suffusate on the tissue since even superficial drying causes rapid cell injury.

A tetranitroblue tetrazolium dye (TNBT) was used to detect superoxide radicals in vivo in Dahl hypertensives, as previously described (Swei et al., 1997, Oxidative stress in the Dahl hypertensive rat. Hypertension 30:1628-33.). In the SHR the number of (EB)-positive nuclei along arterioles or venules (NEB) was determined. At the end of the experiments, the tissue was superfused with absolute ethanol for 10 min followed by EB superfusion to establish the total number of nuclei along the vessel wall (NT). The EB-positive number was computed as EB-positive nuclei = (NEB / NT) x 100 (%) (Suzuki, et al., In-vivo evidence for microvascular oxidative stress in spontaneously hypertensive rats - Hydroethidine microfluorography. 1995, Hypertension 25, 1083-1089).

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