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Effect of sodium metabisulphite on bronchial blood flow in conscious sheep: pharmacological modulation
G M Nichol1, G H Parsons, K F Chung
1Department of Thoracic Medicine, Royal Brompton National Heart & Lung Hospital, London.
Abstract:
1. Sodium metabisulphite (MBS) can induce bronchoconstriction in patients with asthma. We investigated the effects of MBS aerosol on bronchial blood velocity (Vbr) and pulmonary resistance in intubated conscious sheep. 2. Bronchial blood velocity was measured by implanting a 20 MHz ultrasonic Doppler flow probe on the common bronchial branch of the bronchoesophageal artery. 3. Inhaled MBS induced a dose-dependent, transient increase in Vbr lasting for a few minutes without any changes in aortic and pulmonary artery pressures. There was some tachyphylaxis of the Vbr response to successive inhalations of MBS. 4. The cholinoceptor antagonist, ipratropium bromide and the H1 and H2 histamine antagonists, chlorpheniramine and cimetidine, had no significant effect on MBS-induced increase on Vbr. The loop diuretic, frusemide, and the anti-inflammatory drug, nedocromil sodium, which both inhibit MBS-induced bronchoconstriction in patients with asthma, were also without effect. 5. We conclude that MBS induces bronchial vasodilatation in conscious sheep, and that this effect is not dependent on the release of histamine or other mediators, or an activation of cholinergic pathways.
Insights
Sodium metabisulphite (MBS) causes bronchial vasodilation in sheep, not bronchoconstriction. This effect on bronchial blood velocity is not mediated by histamine or cholinergic pathways.
Area of Science:
- Respiratory Physiology
- Pharmacology
Background:
- Sodium metabisulphite (MBS) is known to trigger bronchoconstriction in asthmatic patients.
- The precise mechanism underlying MBS-induced respiratory effects requires further investigation.
Purpose of the Study:
- To investigate the impact of inhaled sodium metabisulphite (MBS) aerosol on bronchial blood velocity (Vbr) and pulmonary resistance.
- To explore the potential mediators involved in MBS-induced airway responses.
Main Methods:
- Utilized intubated conscious sheep as a model.
- Measured bronchial blood velocity (Vbr) using an ultrasonic Doppler flow probe.
- Administered MBS aerosol and various antagonists (ipratropium bromide, chlorpheniramine, cimetidine, frusemide, nedocromil sodium).
Main Results:
- Inhaled MBS caused a dose-dependent, transient increase in Vbr.
- No significant changes were observed in aortic or pulmonary artery pressures.
- Tachyphylaxis in Vbr response to successive MBS inhalations was noted.
- Antagonists and anti-asthma drugs did not affect the MBS-induced Vbr increase.
Conclusions:
- Sodium metabisulphite induces bronchial vasodilation in conscious sheep.
- This MBS-induced vasodilation is independent of histamine release or cholinergic pathway activation.