Abstract
It was reported that cAMP participates in a signaling pathway that couples activation of Gs with ATP release from erythrocytes (RBCs). cAMP levels are the product of adenylyl cyclase (AC) activity and degradation by phosphodiesterases (PDEs). RBCs possess AC activity, however, their PDE activity is poorly characterized. Insulin, a PDE3 activator, decreases cAMP levels in RBCs. Here, we investigate the hypothesis that PDE3B is present and active in RBCs. PDE3B was identified in RBC membranes by Western analysis. RBCs (50% HCT) were incubated with the PGI2 analog, iloprost (ILO, 1 μM), in the absence and presence of selective PDE3 inhibitors. ILO alone produced a 90.3±20.6% increase in cAMP (P<0.05). In the presence of cilostazol (CILO, 30 or 100 μM) or its parent compound, cilostamide (CMDE, 30 μM), basal cAMP levels were unchanged. However, in the presence of 30 and 100 μM CILO, ILO–induced cAMP levels increased from 3.0±0.5 to 5.4±1.1 (n=6, P<0.05) and 3.9±0.6 to 10.2±2.7 (n=7, P<0.05) pmole/1010 RBCs, respectively. In addition, CMDE also potentiated ILO-induced cAMP levels from 3.0±0.7 to 5.1±1.4 pmole/1010 RBCs (n=4, P<0.05). Here we demonstrate that PDE3 is present in RBC membranes and is important in the regulation of ILO-induced increases in cAMP. Inhibition of PDE3B could facilitate ATP release from RBCs in response to physiological stimuli. Funded by NIH grant HL-64180 and ADA grant RA-133.
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