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Effect of intermittent hypoxia on cardiovascular function, adrenoceptors and muscarinic receptors in Wistar rats

Published online by Cambridge University Press:  25 June 2002

R. Germack*
Affiliation:
Laboratoire ‘Réponses cellulaires et fonctionnelles à l’hypoxie’, EA 2363, Université Paris XIII, 93017 Bobigny, France
F. Leon-Velarde
Affiliation:
Laboratoire ‘Réponses cellulaires et fonctionnelles à l’hypoxie’, EA 2363, Université Paris XIII, 93017 Bobigny, France Laboratorio de Transporte de Oxigeno/IIA, Universidad Cayetano Heredia, Lima, Peru
R. Valdes De La Barra
Affiliation:
Laboratorio de Fisiologia de Altura, Universidad Arturo Prat, Iquique, Chile
J. Farias
Affiliation:
Laboratorio de Fisiologia de Altura, Universidad Arturo Prat, Iquique, Chile
G. Soto
Affiliation:
Laboratorio de Fisiologia de Altura, Universidad Arturo Prat, Iquique, Chile
J. P. Richalet
Affiliation:
Laboratoire ‘Réponses cellulaires et fonctionnelles à l’hypoxie’, EA 2363, Université Paris XIII, 93017 Bobigny, France
*
Corresponding author: richalet@smbh.univ-paris13.fr
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Abstract

The usual model of intermittent hypoxia (sleep apnoea) corresponds to repeated episodes of hypoxia from a few seconds to a few hours interspersed with episodes of normoxia. The aim of this study was to evaluate in rats the effect of two periods of intermittent exposure for 2 months to hypoxia (IHX1, 24 h in hypoxia (428 Torr), 24 h in normoxia; IHX2, 48 h in hypoxia (428 Torr), 24 h in normoxia) as a new model of hypoxia simulating intermittent exposure to high altitude experienced by Andean miners. We assessed the haematological parameters, time course of resting heart rate and systolic blood pressure. We also evaluated the expression of adrenergic and muscarinic receptors. IHX1 and IHX2 produced an increase in haematocrit, haemoglobin concentration and mean corpuscular volume as previously seen in most hypoxic models. IHX1 and IHX2 induced a similar sustained elevation of systolic blood pressure (132 ± 2 and 135 ± 3 mmHg, respectively, vs. the control level of 121 ± 16 mmHg) after 10 days of exposure without change in heart rate. Right ventricular (RV) hypertrophy (225 ± 13 and 268 ± 15 mg g−1, vs. 178 ± 7 mg g−1) and downregulation of α1-adrenoceptor (RV: 127 ± 21 and 94 ± 16 fmol mg−1vs. 157 ± 8 fmol mg−1; left ventricle (LV): 141 ± 5 and 126 ± 9 fmol mg−1vs. 152 ± 5 fmol mg−1) have been found in both groups, with right ventricular hypertrophy being greater and α1-adrenoceptor density being lower in IHX2 than in HX1 groups. These data indicate that both parameters are related to the time of exposure to hypoxia. IHX1 and IHX2 produced the same magnitude of upregulation of muscarinic receptors (LV, 60%; RV, 40%), and no change in β-adrenoceptors. In conclusion, exposure to intermittent hypoxia led to polycythaemia and RV hypertrophy as observed in other types of hypoxia. A specific cardiovascular response was seen, that is an increase in blood pressure without change in heart rate, which was different from the one observed in episodic and chronic hypoxia. Furthermore, this model involved specific modifications of α1-adrenergic and muscarinic expression.

Type
Research Article
Copyright
Copyright © Experimental Physiology 2002

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