CHANGES IN SUBSTANCE-P AND VASOACTIVE INTESTINAL POLYPEPTIDE LEVELS IN THE RESPIRATORY-TRACT OF AGING GUINEA-PIGS

Alterations in the levels of substance P (SP)-like and vasoactive intestinal polypeptide (VIP)-like immunoreactivity in the respiratory tract of aging guinea pigs were measured using specific radioimmunoassays (RIAs). Normal Hartley male guinea pigs were classified into four groups by age (4-5 weeks, 13-15 weeks, 12 months and 24 months). The trachea, major bronchus and inferior lung were collected from anesthetized guinea pigs and homogenized in 1 M acetic acid. RIAs were done using synthetic SP and guinea-pig VIP (gpVIP) as standard antigens. In the airway, SP and gpVIP levels decreased with age, with SP being more reduced than gpVIP in the lung and bronchus. These results indicate that the age of guinea pigs should be considered when measuring the content of neuropeptides in the airway. In addition, it is indicated that changes in bronchial hyper-reactivity due to aging or to out-grow phenomenon in asthmatic children are possibly related to neuropeptides.