Changes of agouti-related protein in hypothalamus, placenta, and serum during pregnancy in the rat.

Agouti-related protein (AGRP) is a homolog of the agouti protein and acts as an antagonist of peptides derived from propiomelanocortin through melanocortin receptors. This peptide is produced mainly in the hypothalamus, particularly during negative energy balance and influences increased food intake. In the hypothalamus, this peptide is co-expressed in arcuate nuclei with neuropeptide Y, another important peptide that regulates energy metabolisms. In our study, we analyzed changes in the Agrp mRNA level in the hypothalamus as well as mRNA and protein levels in placenta during different stages of rat pregnancy. We also investigated the AGRP level in the blood serum. In this study, we found the AGRP level in serum increased, while its gene expression in the hypothalamus increased only up to the 13th day of pregnancy, and decreased on the 18th day. This study demonstrates that AGRP is expressed during late pregnancy in placenta. Moreover, we found that AGRP expression is higher on the 18th than on the 13th day of pregnancy. Our results indicate that AGRP may play an important role during pregnancy in the mother's and, possibly, also in the fetus's energy balance.