Figure 3. Preincubation with forskolin does not abolish histamine-induced increases in MLC phosphorylation.

PCA rings were suspended in a muscle bath and equilibrated in Kreb’s bicarbonate buffer for 2 h. Rings were treated with either basal conditions, 5 µM histamine for 3 min, 5 µM forskolin for 10 min followed by 5 µM histamine for 3 min, or 5 µM forskolin for 10 min and snap frozen. Proteins were extracted and loaded on urea glycerol gels to separate the p-MLC and np-MLC and were detected by western blotting using an antibody that recognizes both forms. Panel A: Representative western blot of p-MLC and np-MLC. Panel B: Cumulative data representing the relative amounts of the p-MLC over the total MLC obtained when the phosphorylated and non-phosphorylated bands were quantitated densitometrically n = 4. *significance between Histamine and Basal. ^#significance between Forskolin plusHistamine and Basal.