Characterization of H1- and H2-receptor function in pulmonary and systemic circulations of sheep

T. Ahmed, K. B. Mirbahar, W. Oliver

Research output: Contribution to journalArticle

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Abstract

We investigated the histamine H1- and H2-receptor function in the pulmonary and systemic circulations of sheep by in vivo and in vitro techniques. Combined H1 and H2 stimulation (by intravenous histamine) in vivo increased pulmonary vascular resistance (PVR) to 435% of base line and decreased systemic vascular resistance (SVR) to 49% of base line. Selective H2 stimulation (histamine after chlorpheniramine pretreatment) decreased PVR and SVR to 86 and 82% of base line, respectively, while selective H1 stimulation (histamine after metiamide pretreatment) increased PVR to 424% of base line and decreased SVR to 64% of base line. Combined H1- and H2-antagonist pretreatment completely blocked the effects of histamine on SVR, while PVR still decreased to 85% of base line, suggesting a mild 'atypical' H2-receptor response in the pulmonary circulation under conditions of resting vascular tone. With increased pulmonary vascular tone (hypoxia), histamine decreased PVR to 55% (H1-antagonist pretreatment) and to 58% (combined H1- and H2- antagonist pretreatment) of posthypoxia values, respectively, demonstrating a marked atypical H2-receptor response. In vitro, both pulmonary arterial and venous strips showed a contractile dose-response to histamine, which was blocked by the H1-antagonist pyrilamine (mepyramine). In precontracted strips, both histamine and the H2-agonists (dimaprit and impromidine) elicited a relaxant response, which was neither blocked by H1-antagonist alone nor by combined H1- and H2-antagonists. We conclude that in sheep the histamine-induced pulmonary vasoconstrictor response is mediated by H1-receptors, while the pulmonary vasodepressor response is mediated by atypical H2-receptors. The systemic vasodepressor response is mediated by both H1- and typical H2-receptors.

Original languageEnglish
Pages (from-to)175-184
Number of pages10
JournalJournal of Applied Physiology Respiratory Environmental and Exercise Physiology
Volume53
Issue number1
StatePublished - Jan 1 1982
Externally publishedYes

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Histamine H1 Receptors
Histamine H2 Receptors
Pulmonary Circulation
Vascular Resistance
Sheep
Histamine
Pyrilamine
Lung
Blood Vessels
Impromidine
Dimaprit
Metiamide
Histamine Agonists
Chlorpheniramine
Vasoconstrictor Agents

ASJC Scopus subject areas

  • Endocrinology
  • Physiology

Cite this

Characterization of H1- and H2-receptor function in pulmonary and systemic circulations of sheep. / Ahmed, T.; Mirbahar, K. B.; Oliver, W.

In: Journal of Applied Physiology Respiratory Environmental and Exercise Physiology, Vol. 53, No. 1, 01.01.1982, p. 175-184.

Research output: Contribution to journalArticle

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abstract = "We investigated the histamine H1- and H2-receptor function in the pulmonary and systemic circulations of sheep by in vivo and in vitro techniques. Combined H1 and H2 stimulation (by intravenous histamine) in vivo increased pulmonary vascular resistance (PVR) to 435{\%} of base line and decreased systemic vascular resistance (SVR) to 49{\%} of base line. Selective H2 stimulation (histamine after chlorpheniramine pretreatment) decreased PVR and SVR to 86 and 82{\%} of base line, respectively, while selective H1 stimulation (histamine after metiamide pretreatment) increased PVR to 424{\%} of base line and decreased SVR to 64{\%} of base line. Combined H1- and H2-antagonist pretreatment completely blocked the effects of histamine on SVR, while PVR still decreased to 85{\%} of base line, suggesting a mild 'atypical' H2-receptor response in the pulmonary circulation under conditions of resting vascular tone. With increased pulmonary vascular tone (hypoxia), histamine decreased PVR to 55{\%} (H1-antagonist pretreatment) and to 58{\%} (combined H1- and H2- antagonist pretreatment) of posthypoxia values, respectively, demonstrating a marked atypical H2-receptor response. In vitro, both pulmonary arterial and venous strips showed a contractile dose-response to histamine, which was blocked by the H1-antagonist pyrilamine (mepyramine). In precontracted strips, both histamine and the H2-agonists (dimaprit and impromidine) elicited a relaxant response, which was neither blocked by H1-antagonist alone nor by combined H1- and H2-antagonists. We conclude that in sheep the histamine-induced pulmonary vasoconstrictor response is mediated by H1-receptors, while the pulmonary vasodepressor response is mediated by atypical H2-receptors. The systemic vasodepressor response is mediated by both H1- and typical H2-receptors.",
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