Figure 7. Inhibition of the Ca²⁺ channel in rat cardiomyocytes by haem oxygenase inhibitors with respect to phosphorylation, permeating ion and hypoxia.

A and B, effect of 100 nm ZnPP on I_Ca (A) and I_Ba (B) measured in the absence of phosphorylating interventions (no cAMP, filled circles) and with dialysis of either 0.2 mm cAMP (cAMP, open circles) or 60 nm okadaic acid (OA, open triangles). C, pretreatment with an inhibitor of CaMKII (10 μm CK59) restored the suppressive effect (double arrow) of 100 nm ZnPP on I_Ca in cardiomyocytes dialysed with 0.2 mm cAMP. Notice that in this, as in all our experiments, the suppression of I_Ca was quantified based on a normalization that yielded 100% immediately before the exposure to hypoxia or ZnPP. D, hypoxia (N₂) had no additional suppressive effects after I_Ba had been suppressed by 1 μm ZnPP. E, summary of the quantitative effects of 100 nm ZnPP on I_Ca and I_Ba, as measured in panels A–C. This bar graph has the same layout as used for hypoxic effects in Fig. 3C, but shows data obtained with a different protein kinase inhibitor (CK59 vs. H-89).