ABSTRACT
To determine the effect of Yersinia enterocolitica (YE) enteritis on the contractility of intestinal smooth muscle, rabbits (600–900 g) were divided into infected (n=9) and sham-infected animals fed ad lib (n=9), or pair-fed with the infected group (n=9). Animals were inoculated with 1010 organisms of YE in 10 ml NaHCO3 (infected) or 10 ml NaHCO3 (sham-infected control and pair-fed groups) at time zero. Daily food intake, weight gain, and YE excretion were noted. Animals were sacrificed and longitudinal smooth muscle strips prepared from proximal, medial and distal segments of intestine on day 6. Isometric tension was recorded in tissue baths perfused with oxygenated Krebs and 10−6 M tetrodotoxin. Passive and active (the response to 10−5 M carbachol) length-tension curves were generated. Then with the muscle strips stretched to their optimum length, Lo, the dose-response to carbachol (10−8 to 10−4 M) and to KCI (5–80 mM) was determined. Infected animals had significantly less food intake and weight gain compared to controls. The development of passive tension with stretch and Lo was no different in infected compared with control or pair-fed tissues from the same site. The dose-response curves for tissues equilibrated at Lo and exposed to carbachol or KCI showed that while the ED50s were not significantly different, the response of infected tissues was significantly impaired compared to that of the pair-fed group while the responsiveness of pair-fed tissues was significantly greater than the response of infected or control tissues at any specific site. Thus there was a significantly reduced ability to develop tension in response to carbachol in infected compared to pair-fed animals; while pair-fed tissues (from animals that were only malnourished) exhibited a significantly increased response to carbachol compared to control or infected animals. As the response can be reproduced with KCI depolarization it may reflect post-receptor changes in smooth muscle function.
