Figure 5.

(A) Cells were synchronized, and proliferation was stimulated by l-glutamine, as described in Fig. 2A, and, 21 h later, cells were exposed to PBS or the indicated concentrations of ST (●) or uroguanylin (○). After 15 min of incubation, [³H]thymidine was added to the media, and incubation was continued for another 3 h. [³H]Thymidine incorporation into DNA was determined as described in Materials and Methods. (B) Cells were synchronized, stimulated to proliferate, and exposed to 1 μM ST (■) or PBS (□), as described in A. After 3 h of incubation, media was aspirated, and cGMP and cAMP were quantified as described in Materials and Methods. Data from a single experiment are expressed as fold accumulation in ST-treated compared with PBS-treated cells (control; CTR). (C) Cells were synchronized, stimulated to proliferate, and pulse labeled with [³H]thymidine, as described in A, and, 15 min later, T84 cells were exposed to PBS (CTR), 1 μM TJU 1-103 (TJU), 1 μM ST, 1 μM uroguanylin (URO), 5 mM 8-Br-cGMP, 10 μM zaprinast (ZAP), or 1 μM ST plus 10 μM zaprinast. After 3 h of incubation, [³H]thymidine incorporation into DNA was quantified as described in Materials and Methods. Results are the mean ± SEM of a representative experiment performed in triplicate. *, P < 0.05; **, P < 0.01; ***, P < 0.001.