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Pulmonary vascular responsiveness in cold-exposed calves
Canadian Journal of Physiology and Pharmacology
|February 1, 1985
Summary
Cold exposure increases pulmonary venous resistance in calves, but does not alter responses to hypoxia, histamine, or 5-hydroxytryptamine (5-HT). This suggests mild cold does not increase overall pulmonary vascular reactivity.
Area of Science:
- Cardiovascular Physiology
- Environmental Physiology
- Pulmonary Circulation
Background:
- Pulmonary vascular responses are critical for oxygen transport.
- Environmental factors like temperature can influence cardiovascular function.
- Understanding cold exposure effects on pulmonary hemodynamics is important.
Purpose of the Study:
- To investigate the effects of acute, mild cold exposure on pulmonary vascular responses in unanesthetized bull calves.
- To determine if cold exposure alters pulmonary vascular reactivity to hypoxia, histamine, and 5-hydroxytryptamine (5-HT).
Main Methods:
- Recorded pulmonary and systemic arterial pressures, and left atrial pressures in bull calves.
- Exposed calves to neutral (16-18°C) and cold (3-5°C) temperatures.
- Administered hypoxia, histamine, and 5-HT infusions under both temperature conditions.
Main Results:
- Cold exposure significantly increased pulmonary arterial wedge pressure and pulmonary venous resistance.
- Hypoxia responses (increased pressures, heart rate, respiratory rate) were similar in cold and neutral conditions.
- Responses to histamine and 5-HT infusions were not significantly different between cold and neutral temperatures.
Conclusions:
- Acute, mild cold exposure increases resistance in the pulmonary venous circulation.
- Cold exposure does not generally increase pulmonary vascular reactivity to hypoxia, histamine, or 5-HT.
- Pulmonary venoconstriction during cold is not mediated by enhanced reactivity to common vasoactive agents.