Expression of C-Type Natriuretic Peptide in Human Placenta and Myometrium in Normal Pregnancies and Pregnancies Complicated by Intrauterine Growth Retardation

OBJECTIVE: C-type natriuretic peptide (CNP) is a vasoactive hormone and the endothelial component of the natriuretic peptide system. At present, nothing is known about CNP expression in human reproductive tissue. Since CNP shows antimitogenic and vasodilatative properties, it was the aim of the study to investigate whether CNP expression is altered in placenta and myometrium from pregnancies complicated by intrauterine growth retardation. METHODS: CNP expression was examined by RNase protection assay in human placenta and myometrium from six normal term pregnancies, six pregnancies with preterm delivery and six pregnancies complicated by intrauterine growth retardation (IUGR). RESULTS: In placenta and myometrium, CNP expression levels did not differ between term and preterm pregnancies (40 vs. 28 weeks of gestation). In pregnancies with IUGR (34 weeks of gestation) placental CNP expression was significantly decreased (100.00 +/- 18.6 vs. 67.09 +/- 8.7; p < 0.05). In the myometrium from IUGR pregnancies CNP expression was significantly increased to 191.48 +/- 42.5 (vs. 100.00 +/- 15.4; p < 0.05). CONCLUSIONS: CNP is expressed in human placenta and myometrium with no dependency on gestational age in the third trimester. Pregnancies with IUGR show an opposite regulation of CNP in placenta and myometrium, which indicates an organ-specific function of the peptide in human reproductive tissue.