EFFECTS OF GIARDIA-LAMBLIA INFECTION ON GASTROINTESTINAL TRANSIT AND CONTRACTILITY IN MONGOLIAN GERBILS

To determine if Giardia lamblia infection is associated with altered g astrointestinal transit and smooth muscle contractile function, Mongol ian gerbils were infected orogastrically with 2 x 10(5) trophozoites ( infected) or vehicle (uninfected controls). At the time of peak coloni zation, control and infected animals were infused either orogastricall y or intraduodenally with Cr-51. Gastric emptying of isotope and intes tinal transit (measured by the geometric center of distribution of int estinal Cr-51 transit) were significantly (P < 0.05) greater in the in fected compared to control animals in both the fasted and the fed stat es. Then, to determine whether Giardia lamblia has an effect on the co ntractility of longitudinal and circular smooth muscle, isometric tens ion of jejunal segments was recorded. The development of active tensio n with stretch and the dose-response curve to bethanechol were signifi cantly increased in the longitudinal muscle of infected animals compar ed to controls. However, the circular smooth muscle did not show a sim ilar increase in contractility. These findings suggest that an altered gastrointestinal transit and smooth muscle contractility may be invol ved in the pathophysiology of giardiasis.