The effect of heparin on pregnancy associated plasma protein-A concentration in healthy, non-pregnant individuals

Objectives: The objective of this study was to determine the differences in pregnancy associated plasma protein-A (PAPP-A) concentrations in heparin naive and heparin treated healthy men and non-pregnant women, to find a possible difference in different age groups, and to determine the response in PAPP-A concentration to repeated injections of unfractionated heparin. Design and methods: Twenty-five healthy, non-pregnant volunteers divided into five groups (determined by gender and age) received 5000. IU unfractionated heparin intravenously. Five young men received an additional 5000. IU after 90 and 180. min. Blood samples to determine PAPP-A concentration and APTT were drawn at different time points. Results: Injection of heparin elicited increase in and rapid normalization of PAPP-A concentrations in all subjects. The group of 20-30-year-old never-pregnant women had lower responses than the individuals of the four other groups. The difference was not significant (p>. 0.05). Repeated injections of heparin caused additional peaks in PAPP-A concentration of about the same sizes as the first peak. We observed an increase in time to normalization of PAPP-A concentration (from 75-90. min to 90-150. min) and APTT levels with repeated injections. Conclusions: We observed a rapid normalization of PAPP-A. Our result has a great similarity to the half-life of unfractionated heparin. This result combined with the finding of equally sized peaks in PAPP-A concentration, and that all of this was found in healthy, non-pregnant individuals, suggests that heparin might compete for a binding-site on PAPP-A or with PAPP-A itself for a common receptor in healthy arterial vessels.