Studies on the half-life of Schwangerschaftsprotein 1 (SP1)

The disappearance rate of Schwangerschaftsprotein 1 in normal and pathological pregnancies

In six women with a normal vaginal delivery at term, in 12 women who had a suction curettage between 6 and 12 weeks gestation and in eight women with an ectopic pregnancy, the post-partum or the post-surgery decline in radioimmunoassayable SP1 was faster during the first 24 h after surgery or delivery than later, so that two half-lives were calculated. The first 'half-life' of about 20 h (0-24 h after delivery or surgery) was of the same order of magnitude in all groups studied and corresponded well to previously published values. The mean second 'half-life' (greater than 24 h after delivery or surgery) was significantly longer in term (72.2 h) and in ectopic pregnancies (64.1 h) than in first trimester pregnancies (45.5 h). These results might indicate that the metabolism of SP1 either changes during pregnancy or that the changing SP1 beta/SP1 alpha ratio during pregnancy markedly influences the levels of SP1 as measured by radioimmunoassay.

Postpartum decline in serum concentration of placental proteins in an abdominal pregnancy

The alpha and the beta forms of Schwangerschaftsprotein 1 (SP1) and chorionic gonadotrophin (hCG) were measured after delivery in an abdominal pregnancy with the placenta left in situ. All three proteins declined more slowly than after normal delivery; the half-lives ranging from 6.2-6.5 days. Traces of the proteins could still be detected in the maternal circulation 9 weeks after delivery. These findings are construed as further support for the belief that the placenta plays a major role in the synthesis of these proteins.

Periovulatory secretion of immunoactive pregnancy-specific beta 1-glycoprotein (SP1) in humans: comparison with "normal" SP1

The pregnancy-specific beta 1-glycoprotein (SP1)-immunoreacting material in serum from two patients around ovulation was compared with serum SP1 activity derived from normal pregnant women. This was done by antibody binding experiments, density gradients and binding to lentil lectin. Periovulatory SP1 behaved similarly to SP1 from pregnant patients. It is therefore suggested that the periovulatory immunoreacting material is true SP1 and that this protein, though rarely, can be synthesized outside the trophoblast in healthy women.