Journal
AMERICAN JOURNAL OF PHYSIOLOGY-HEART AND CIRCULATORY PHYSIOLOGY
Volume 293, Issue 6, Pages H3246-H3253Publisher
AMER PHYSIOLOGICAL SOC
DOI: 10.1152/ajpheart.00957.2007
Keywords
superoxide dismutase; nitric oxide synthase; sympathetic nervous system; catalase; adenosine 5 '-triphosphate-activated potassium channels
Funding
- NHLBI NIH HHS [HL 68686-01] Funding Source: Medline
- NIDDK NIH HHS [DK 49870, T30 DK 59274, DK 36079] Funding Source: Medline
- NIGMS NIH HHS [T30 GM 8386] Funding Source: Medline
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Acute intravenous Tempol reduces mean arterial pressure (MAP) and heart rate (HR) in spontaneously hypertensive rats. We investigated the hypothesis that the antihypertensive action depends on generation of hydrogen peroxide, activation of heme oxygenase, glutathione peroxidase or potassium conductances, nitric oxide synthase, and/or the peripheral or central sympathetic nervous systems (SNSs). Tempol caused dose-dependent reductions in MAP and HR (at 174 mu mol/kg; Delta MAP, -57+/- 3 mmHg; and Delta HR, -50 +/- 4 beats/min). The antihypertensive response was unaffected by the infusion of a pegylated catalase or by the inhibition of catalase with 3-aminotriazole, inhibition of glutathione peroxidase with buthionine sulfoximine, inhibition of heme oxygenase with tin mesoporphyrin, or inhibition of large-conductance Ca2+ -activated potassium channels with iberiotoxin. However, the antihypertensive response was significantly (P < 0.01) blunted by 48% by the activation of adenosine 5'-triphosphate-sensitive potassium (K-ATP) channels with cromakalim during maintenance of blood pressure with norepinephrine and by 31% by the blockade of these channels with glibenclamide, by 40% by the blockade of nitric oxide synthase with N-omega-nitro-L-arginine methyl ester (L-NAME), and by 40% by the blockade of ganglionic autonomic neurotransmission with hexamethonium. L-NAME and hexamethonium were additive, but glibenclamide and hexamethonium were less than additive. The central administration of Tempol was ineffective. The acute antihypertensive action of Tempol depends on the independent effects of potentiation of nitric oxide and inhibition of the peripheral SNS that involves the activation of KATP channels.
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