Radioimmunoassay of saliva estrone sulfate in pregnant sows.

The aim of this study was to establish radioimmunoassay (RIA) for saliva estrone sulfate (E1S), and to elucidate changes in saliva E1S during pregnancy in the sow. Saliva E1S was extracted using a commercially available solid phase column, and the E1S fraction obtained was subjected to RIA. The sensitivity of the RIA was 29.7 pg/tube. The intra- and inter-assay coefficients of variation were 5.5-8.4% and 13.1-19.5%, respectively. Mean recovery for E1S added to saliva samples was as high as 99.9%. A significant positive correlation (r = 0.54, n = 69, p < 0.01) existed between saliva and plasma E1S concentrations. During gestation, the changing patterns of saliva and plasma E1S concentrations were essentially the same, and two peaks of E1S concentrations were observed, one around day 30 and another just before parturition, although E1S concentrations in saliva remained at only 2.4-38.1% (mean 11.4%) of those in plasma E1S. Thus, the present study has made it possible to measure saliva concentrations of E1S and demonstrated a high degree of positive correlation between saliva and plasma E1S concentrations. These results suggest that diagnosis of early pregnancy and of normal or abnormal fetal development could be made by measurements of E1S in saliva.