Figure 7.

cAMP accumulation in lung tissue of PDE4D^+/+ and PDE4D^−/− mice. Slices of lung tissue from PDE4D^+/+, PDE4D^+/−, and PDE4D^−/− mice were preincubated for 15 min in MEM tissue culture medium containing 10 mM Hepes (pH 7.4). After preincubation, 20 μM isoproterenol in the absence or presence of 10 μM carbachol was added to the tubes. Control samples received vehicle only. Incubation was terminated after 15 min by the addition of trichloroacetic acid to a final concentration of 5% (vol/vol). The tissue slices were homogenized and extracts were clarified by centrifugation. The concentration of cAMP in the acid extracts was measured by RIA after acetylation of the samples. Concentrations were corrected for the amount of protein in the extracts. Each point is the mean ± SE of five mice each assayed in triplicate. ∗, P < 0.05