While the complete physiology of activin, FS, and inhibin is not yet understood, there is now clear evidence that alterations in serum activin and inhibin levels are associated with abnormal pregnancy states, such as preeclampsia; therefore, changes in urine FS during pregnancy may reflect pathological alterations in normal activin/ inhibin function. proventil inhaler
While significant differences exist in the FS complexes present in the nonpregnant and pregnant biological samples, our data did not demonstrate any significant change in overall FS levels in the pituitary or ovarian homogenates across the estrous cycle. In a previous study, Besecke et al. demonstrated that pituitary FS levels decreased and then peaked in proestrus. The discrepancy in results may be attributable to limited time points in our sampling such that the peaks and valleys are not detected, or perhaps to a decreased sensitivity of the Western technique when compared to an RIA. The other possibility is that since the prior study was based upon pituitary extracts from tissues that had been perfused, while our data are derived from tissue homogenates, the discrepancy may be related to the presence of cellular-bound forms of FS.