Mechanism of the pulmonary vasoconstrictor action of digoxin in the dog

T. E. Mecca, J. T. Elam, Robert William Caldwell

Research output: Contribution to journalArticle

6 Citations (Scopus)

Abstract

The pulmonary vascular effects of a subarrhythmic dose of digoxin (60 μg/kg i.v.) were examined in the canine in situ perfused lung. Digoxin produced an increase in pulmonary vascular resistance (66.1%) and pulmonary arterial pressure (8.2 mm Hg) at 70 min after injection in the constant-flow, blood-perfused lung preparation. The digoxin-treated group exhibited higher plasma levels of norepinephrine compared with control dogs. The pulmonary vasoconstrictor response to digoxin was abolished by prior treatment with the α-adrenergic antagonists phenoxybenzamine and phentolamine. This vasoconstriction does not involve inhibition of synthesis or action of vasodilator prostaglandins by digoxin, as pretreatment with indomethacin did not attenuate, and even tended to increase, the pressor response to digoxin. The response was prevented by prior treatment with blockers of nonneuronal uptake of catecholamines normetanephrine and hydrocortisone, but not with cocaine, a blocker of neuronal uptake. In the lung preparation perfused with Krebs buffer solution, digoxin failed to produce vasoconstriction when administered intravenously (60 μg/kg) or in the perfusate at a concentration of 8 ng/ml, the blood level at the peak of the pressor response. Sodium-pump activity (ouabain-sensitive 86Rb+ uptake) of intralobular pulmonary arteries excised after 90 min of exposure to digoxin was the same as activity in arteries from control dogs. In conclusion, digoxin produces a pulmonary vasoconstriction through an α-adrenergic mechanism. Since the pressor response was observed only in the blood-perfused lung, blood-borne catecholamines are apparently involved.

Original languageEnglish (US)
Pages (from-to)833-840
Number of pages8
JournalJournal of Cardiovascular Pharmacology
Volume7
Issue number5
DOIs
StatePublished - Jan 1 1985
Externally publishedYes

Fingerprint

Digoxin
Vasoconstrictor Agents
Dogs
Lung
Vasoconstriction
Catecholamines
Normetanephrine
Phenoxybenzamine
Sodium-Potassium-Exchanging ATPase
Adrenergic Antagonists
Phentolamine
Ouabain
Vasodilator Agents
Cocaine
Indomethacin
Vascular Resistance
Adrenergic Agents
Pulmonary Artery
Prostaglandins
Blood Vessels

Keywords

  • Digoxin
  • Dog
  • Pulmonary
  • Vasoconstriction

ASJC Scopus subject areas

  • Pharmacology
  • Cardiology and Cardiovascular Medicine

Cite this

Mechanism of the pulmonary vasoconstrictor action of digoxin in the dog. / Mecca, T. E.; Elam, J. T.; Caldwell, Robert William.

In: Journal of Cardiovascular Pharmacology, Vol. 7, No. 5, 01.01.1985, p. 833-840.

Research output: Contribution to journalArticle

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AB - The pulmonary vascular effects of a subarrhythmic dose of digoxin (60 μg/kg i.v.) were examined in the canine in situ perfused lung. Digoxin produced an increase in pulmonary vascular resistance (66.1%) and pulmonary arterial pressure (8.2 mm Hg) at 70 min after injection in the constant-flow, blood-perfused lung preparation. The digoxin-treated group exhibited higher plasma levels of norepinephrine compared with control dogs. The pulmonary vasoconstrictor response to digoxin was abolished by prior treatment with the α-adrenergic antagonists phenoxybenzamine and phentolamine. This vasoconstriction does not involve inhibition of synthesis or action of vasodilator prostaglandins by digoxin, as pretreatment with indomethacin did not attenuate, and even tended to increase, the pressor response to digoxin. The response was prevented by prior treatment with blockers of nonneuronal uptake of catecholamines normetanephrine and hydrocortisone, but not with cocaine, a blocker of neuronal uptake. In the lung preparation perfused with Krebs buffer solution, digoxin failed to produce vasoconstriction when administered intravenously (60 μg/kg) or in the perfusate at a concentration of 8 ng/ml, the blood level at the peak of the pressor response. Sodium-pump activity (ouabain-sensitive 86Rb+ uptake) of intralobular pulmonary arteries excised after 90 min of exposure to digoxin was the same as activity in arteries from control dogs. In conclusion, digoxin produces a pulmonary vasoconstriction through an α-adrenergic mechanism. Since the pressor response was observed only in the blood-perfused lung, blood-borne catecholamines are apparently involved.

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