Everted portal vein: a sensitive model for studies of vasoactive compounds.

Three preparations of the rat hepatic portal vein, everted, noneverted, and longitudinal strip, were examined for their responsiveness to noradrenaline (NA), substance P (SP), and eledoisin (ED). The longitudinal strips and the everted veins exhibited similar sensitivities to these compounds, whereas the noneverted vein was two to four times less sensitive. The time course to generation of a maximal response was markedly slower for the noneverted vein. The poor reactivity of the noneverted vein is attributed to a reduced accessibility of the compounds to receptor sites. The myogenic responses of the longitudinal strips to NA and ED but not SP were characterized by a tonic-type contracture, whereas everted and noneverted preparations responded to the peptides, at low and intermediate concentrations, with large-amplitude and long-duration contractions. The everted vein is presented as a useful preparation for evaluation of drug-receptor interactions.