IMMUNOCHEMICAL LOCALIZATION OF TYPE-I VIP RECEPTOR AND NK-1-TYPE SUBSTANCE-P RECEPTOR IN RAT LUNG

Peptidergic nerves in the respiratory tract release vasoactive intesti nal peptide (VIP) and substance P (SP), which mediate physiological an d immune functions. Antipeptide antibodies to type I VIP receptor (VIP R) and NK-1-type SP receptor (SPR) were used to identify these recepto rs in normal rat lungs. VIPRs and SPRs were detected on airway epithel ium from the trachea to the respiratory bronchioles but not in alveoli , submucosal glands, or pulmonary smooth muscle, except for that of so me pulmonary veins. VIPRs also were expressed on macrophages around ca pillaries, in tracheal and bronchial connective tissue, in alveolar wa lls, and in the subintima of pulmonary veins and some arterioles. The absence of receptors from airway smooth muscle and submucosal glands i mplies that mediation of some known effects of SP and VIP may be epith elial or macrophage dependent. Other types of VIPRs and SPRs on airway glands and smooth muscle may transduce direct effects. The similar lo calization of VIPRs and SPRs in rat lung suggests that VIP and SP may coordinately regulate some pulmonary functions.