TYPE-I AND TYPE-III PROCOLLAGEN PROPEPTIDES IN AMNIOTIC-FLUID OF NORMAL PREGNANCIES AND IN A CASE OF MILD OSTEOGENESIS IMPERFECTA

Background The propeptides derived from type I and III procollagens, P ICP, PINP and PIIINP, indicate the synthesis of the corresponding coll agens. Their circulating concentrations reflect the growth velocity in infants and children Methods We measured these propeptides in 145 sam ples of amniotic fluid of normal pregnancy. In addition, we have analy sed an amniotic fluid and serum sample hom a mother with osteogenesis imperfecta,:and later the infant's serum sample was also collected for procollagen propeptide analysis. Results High concentrations of prope ptides, 100-1000 times higher than those in adult serum, were found in early second trimester, decreasing significantly towards term, reflec ting the decreased foetal growth rate. Interestingly, the amino-termin al propeptide of type I procollagen, PINP, decreased more that the cor responding carboxy-terminal propeptide, PICP, although both are in pri nciple derived from the same protein. At both stages of pregnancy, the discrepant ratio of PICP to PINP indicated a molar excess of PINP. Ab normally low concentrations of PICP and PINP with normal PIIINP concen trations measured in amniotic fluid and in the serum indicated decreas ed synthesis of type I procollagen in a foetus/infant with mild osteog enesis imperfecta. Conclusions Our data show a decrease in collagen sy nthesis with the stage of pregnancy and lower values of type I procoll agen propeptides in a case of OI.