Endothelinergic Contractile Hyperreactivity in Rat Contralateral Carotid to Balloon Injury: Integrated Role for ETB Receptors and Superoxide Anion

Temporal consequences of neurocompensation to balloon injury on endothelinergic functionality in rat contralateral carotid were evaluated. Rats underwent balloon injury in left carotid and were treated with CP-96345 (NK1 antagonist). Concentration-response curves for endothelin-1 were obtained in contralateral (right) carotid at 2, 8, 16, 30, or 45 days after surgery in the absence or presence of BQ-123 (ETA antagonist), BQ-788 (ETB antagonist), or Tempol (superoxide-dismutase mimic). Endothelin-1-induced calcium mobilization was evaluated in functional assays carried out with BQ-123, BQ-788, or Tempol. Endothelin-1-induced NADPH oxidase-driven superoxide generation was measured by lucigenin chemiluminescence assays performed with BQ-123 or BQ-788. Endothelin-1-induced contraction was increased in contralateral carotid from the sixteenth day after surgery. This response was restored in CP-96345-treated rats. Endothelium removal or BQ-123 did not change endothelin-1-induced contraction in contralateral carotid. This response was restored by BQ-788 or Tempol. Contralateral carotid exhibited an increased endothelin-1-induced calcium mobilization, which was restored by BQ-788 or Tempol. Contralateral carotid exhibited an increased endothelin-1-induced lucigenin chemiluminescence, which was restored by BQ-788. We conclude that the NK1-mediated neurocompensatory response to balloon injury elicits a contractile hyperreactivity to endothelin-1 in rat contralateral carotid by enhancing the muscular ETB-mediated NADPH oxidase-driven generation of superoxide, which activates calcium channels.

Effects of hypericin on the oxidative stress and modulation of cytochrome P450 (CYP1A) activity in microsomes

Hypericin is a pigment present in the widely distributed medicinal plant Hypericum perforatum L. (Hypericaceae). In our research, hypericin was found to be an inhibitor of NADPH/Fe2+ induced microsomal lipid peroxidation and NADPH-dependent lucigenin chemiluminescence emission in vitro. Hypericin also inhibited the microsomal CYP1Adependent 7-ethoxyresorufin O-deethylase (EROD) which participates in the metabolic activation of xenobiotics including chemical carcinogens.

Abstract P081: Tempol Decreases Blood Pressure in Aged Female SHR When Treated With Acetazolamide

Oxidative stress contributes to the development and maintenance of hypertension in male rodents, but studies in females have rarely shown a reduction in blood pressure (BP) with antioxidants. Tempol, a superoxide dismutase mimetic, decreases BP in young male SHR, but fails to reduce BP in either young or old female SHR, despite the fact that females have similar or higher levels of oxidative stress markers. The reason for the sex difference in the response to tempol remains unclear. Acetazolamide inhibits carbonic anhydrase in the proximal tubule thus increasing sodium delivery to the distal nephron, and thereby should increase distal oxidative stress. Acetazolamide was used to test the hypothesis that with increased sodium delivery to the distal nephron, tempol would reduce the BP in aging female SHR. Female SHR, 20-22 mos old, were divided into three groups (n=4-6/grp): Control (C), Acetazolamide (A), and Acetazolamide+Tempol (A+T). After baseline mean arterial pressure (MAP; telemetry), rats received vehicle (C) or acetazolamide (A and A+T). On day 8, rats in C and A+T groups were given tempol (30 mg/kg) for 11 days. Baseline MAP was similar (C: 170±7; A: 182±4; A+T: 172±6 mm Hg, p=NS). Tempol had no effect on MAP in C+T, but reduced MAP in A+T group (C+T: 169±1; A: 171±1; A+T: 151±5 mm Hg; p<0.005 A+T vs A, C+T). Basal renal oxidative stress measured by lucigenin chemiluminescence was not different in the groups; NADPH-stimulated oxidative stress was decreased in A+T compared to A and C+T (C+T: 641.8±72.2; A: 499.3±18.3; A+T: 406.2±56.3 RLU/mg/min; p<0.05, A+T vs A, C+T). Plasma total antioxidant capacity was increased by tempol only in A+T rats (C+T: 59.07±9.67; A: 69.01±4.66; A+T: 118.24±18.38 nmol/μl; p<0.05, A+T vs A, C+T). Thus tempol is capable of modestly reducing MAP in aging female SHR when proximal sodium reabsorption is blocked. The data suggest that oxidative stress-mediated BP control is dependent on increased sodium delivery to the distal nephron. Because hypertension in male SHR is attenuated with tempol alone, but not in females, taken together, the data suggest sex differences in sodium handling and thus localization of oxidative stress production in the kidneys of SHR. Supported by NIH-R01HL66072, PO1HL51971 (JFR), 14POST18640015 (ROM).