Amniotic fluid laminin and type IV collagen in normal and pathological pregnancies

Specific radioimmunoassays for the fragment P1 of human laminin and the 7-S collagen domain of human type IV collagen were used to quantify these basement membrane proteins in second trimester amniotic fluid samples from 21 normal and 41 pathological pregnancies, the latter group being defined by elevated amniotic fluid alpha-foetoprotein (AFP) or abnormal foetal karyotype, or both. The mean laminin P1 concentration in the normal 15 to 18-wk pregnancies was 36 micrograms/l (range 10-77) and that of the 7-S collagen was 46 micrograms/l (range 7-152). The molecular size of the antigens in amniotic fluid from both normal and pathological pregnancies, when assessed by gel filtration was very large, probably representing intact laminin and type IV collagen. Pathological pregnancies, e.g. cases of Turner syndrome, Meckel syndrome and anencephaly often had elevated amniotic fluid laminin and type IV collagen concentrations. A weak, but nevertheless significant, correlation was found between the amniotic fluid laminin and type IV collagen concentrations and also between type IV collagen and AFP, but none between laminin and AFP. In eight pregnancies with foetuses suffering from the congenital nephrotic syndrome of the Finnish type, a genetic disease assumed primarily to involve some component of the glomerular basement membrane, the amniotic fluid concentrations of both laminin and type IV collagen were within normal limits in spite of an elevated amniotic fluid AFP.