Atrazine inhibits cAMP-specific PDEs in perifused pituitary cells. A, Concentration-dependent effects of atrazine on cAMP release in cells perifused with IBMX-free medium. B, The lack of effects of atrazine on cAMP release in cells bathed in 1 mM IBMX-containing medium. Notice a 10-fold increase in cAMP release compared to A. C, Comparison of effects of atrazine and IBMX on cAMP release. D, The lack of effects of atrazine on cGMP release in cells bathed in IBMX-free medium. In A, B, and D, horizontal bars indicate duration of atrazine application, and in C duration of atrazine or IBMX application. The data shown are representative of 3–4 similar experiments.