FIGURE 3.

GA but not NECA inhibits CT intoxication. A, CHO cells were incubated with varying concentrations of CT in the absence of additional treatment, in the presence of 0.1 μm GA, or in the presence of 0.1 μm NECA. After 2 h of continual toxin exposure, toxicity was assessed from the elevated levels of intracellular cAMP. The means ± S.E. of at least four independent experiments with triplicate samples are shown. B, CHO cells were incubated for 4 h with varying concentrations of ricin in the absence or presence of 0.1 μm NECA. Toxicity was then determined from the incorporation of [³⁵S]methionine into newly synthesized proteins. The averages ± ranges of two independent experiments with triplicate samples are shown. C, surgically sealed sections of rat intestine were injected with 2 μg/ml of CT in the absence or presence of 15 μm GA. Two other loops were injected with only 15 μm GA or with PBS. Morphological examination (inset) and the calculation of fluid accumulation were performed 7 h post-injection. Results presented in the graph represent the averages ± S.D. of data obtained from 4 rats.