FIGURE 2.

Neither soluble guanylyl cyclase activation nor cyclic nucleotide phosphodiesterase inhibition mediates cGMP elevation by 17β-estradiol. Specific inhibitors were applied to intact rat hepatocytes to investigate the involvement of soluble guanylyl cyclase and cyclic nucleotide phosphodiesterases in the elevation of cGMP by 17β-estradiol. Cells were incubated at 37 °C. Total cGMP levels were measured by enzyme immunoassay. All data shown are the mean values of at least six experiments from at least three independent hepatocyte preparations. A, 17β-estradiol does not stimulate soluble guanylyl cyclase. Cells were incubated with either no treatment (control) or soluble guanylyl cyclase inhibitor NS2028 (10 μm) for 5 min. 10 nm water-soluble 17β-estradiol (E2), 200 nm ANP, or 100 nm sodium nitroprusside (SNP) was then added, and cells were incubated for a further 5 min. *, significantly different from control; **, significantly different from NS2028 alone. B, 17β-estradiol does not elevate cGMP through inhibition of cyclic nucleotide phosphodiesterases. Cells were incubated with either no treatment (control) or 300 μm IBMX plus 300 μm zaprinast (zap) for 10 min. 10 nm water-soluble 17β-estradiol (E2) or no treatment were then added, and cells were incubated for a further 5 min. *, significantly different from control; **, significantly different from control plus IBMX and zaprinast.