The particular affinity of FS for activin and inhibins may also vary on the basis of specific conditions, such as differing pH milieu or differing amounts of a2 macroglobulin (a low-affinity, large-capacity activin-binding protein) in different organ systems, thereby altering the balance of activin/inhibin action as well as the actions of other related proteins such as TGF-p, which has been reported to oppose the actions of activin in human trophoblast cells, possibly via alterations in FS. Buy Advair Diskus Online
Significant changes in serum activin and FS occur during pregnancy. Specifically, levels of activin A increase in serum from both the pregnant human and rat during the third trimester or its equivalent.. Total FS increases during gestation but free FS remains unchanged. These observations led to the study of FS complexes in the pregnant kidney and urine. The presence of these complexes in third-trimester pregnant urine and its absence in the nonpregnant urine are consistent with the evidence that there are significantly more FS complexes in the pregnant rat kidney in comparison to the nonpregnant kidney. The inability to clearly detect an FS-inhibin complex in nonpregnant human or rat urine suggests two possibilities: the amounts present are below the limits of the Western or ELISA assays, or the protein is not present in the nonpregnant state.