Altered Vascular Responsiveness in Isolated Perfused Lungs from Aging Rats

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Abstract
Systemic vascular hyporesponsiveness is well documented in aged rats, but a similar decreased vasoreactivity of the pulmonary vasculature has not been reported. Isolated lungs from young (3-5 mo.) and middle-aged (12-14 mo.) rats were perfused with whole blood and challenged alternately with alveolar hypoxia, angiotensin II and 5-hydroxytryptamine. Hypoxic pulmonary vasoconstriction was less in the aging rats during 5- and 10-min hypoxic exposures. Log-dose response curves for angiotensin II and 5-hydroxytryptamine were right-shifted in the aging rats, indicating decreased responsiveness to the vasoactive agents. Since the vascular responses to all 3 vasoconstrictors were lower in the older animals, a generalized pulmonary vascular hyporeactivity with advancing age is suggested.