Effect of Yersinia enterocolitica ST on Cyclic Guanosine 3′, 5′‐Monophosphate Levels in Mouse Intestines and Cultured Cells

We determined the effect of heat‐stable enterotoxin produced by Yersinia enterocolitica (Y. enterocolitica ST) on cyclic nucleotide levels in the intestines of 6‐day‐old mice and in cultured cell line cells. The concentration of cyclic guanosine 3′,5′‐monophosphate (cyclic GMP) in homogenates of the intestines increased four‐ to fivefold by 3 min after intragastric administration of 10 units of purified Y. enterocolitica ST. This increase continued for 60 min, and then the concentration of cyclic GMP fell toward the levels of the controls. On the other hand, fluid accumulation in the intestines was not evident until 60 min after administration of the toxin. Thus, the increase in intestinal cyclic GMP concentration preceded measurable fluid accumulation. The effect on both cyclic GMP levels and fluid accumulation was abolished by treatment of the ST with either alkali solution (pH 10.7) or 2‐mercaptoethanol. Likewise, cyclic GMP levels in cultured cells (CCL‐6, HeLa, L, and Mm‐1 cells) increased dose‐dependently by 10 min after incubation of the cells with the ST. Cyclic adenosine 3′,5′‐monophosphate levels in both intestines and cultured cells were not affected by the toxin.