FIGURE 4.

Effect of tetanus toxin on cAMP-stimulated renin release and total renin content. A, renin release is shown. After pretreatment of JG cells with vehicle (black bars) or tetanus toxin (gray bars) as described in Fig. 3, JG cells were serum-deprived for 2 h followed by treatment with vehicle (CONT) or forskolin (10 μm) plus IBMX (0.5 mm) for 1 h to stimulate cAMP levels as indicated in x axes. Cell culture supernatants were collected for measurement of renin release as described under “Experimental Procedures.” Attached cells in the culture dishes were lysed in 0.1% Triton X and centrifuged, and supernatants were collected for measurement of total renin content. Renin release is expressed as a percentage of the total renin content. Data are expressed as the mean ± S.E. *, p < 0.01, CONT versus forskolin/IBMX; #, p < 0.05, forskolin/IBMX versus tetanus toxin + forskolin/IBMX; n = 4. B, shown is the effect of tetanus toxin on total renin content in JG cells. Total renin content values are corrected by protein concentration (ng of ANGI/h of incubation/mg of protein). Data are expressed as the mean ± S.E. (n = 4; p = ns).