Figure 1.

Effect of exogenous LTD₄ or PMA challenge on isoproterenol-induced cAMP accumulation in HASMC. A-B. Effects of leukotriene D₄ (LTD₄, 10^-6M) challenge and pretreatment with the CysLT₁R antagonist montelukast (MK, 10^-6M) on cAMP accumulation induced by multiple (A) and single (B, 10^-5M) isoproterenol concentrations in HASMC. C. Effect of phorbol-12-myristate-13-acetate (PMA, 5 × l0^-7M) challenge and pretreatment with the PKC inhibitor GF109203X (10^-6M) on cAMP accumulation induced by 10^-5M isoproterenol in HASMC. The results are presented as mean ± S.E.M. of at least three experiments performed in triplicate. **P < 0.01 (one-way ANOVA).