Maternal Serum Hormone Concentrations in Long-Evans Rats

Abstract The purpose of this study was to determine the effect of pregnancy on serum concentrations of estradiol, progesterone and prolactin in Long-Evans rats. Female Long-Evans rats, both pregnant and non-pregnant, were used. Four groups (n = 10 rats in each group) were studied: Non-pregnant rats; pregnant rats at 7, 14, and 20 gestational days. Maternal blood was collected transcardially, and serum estradiol, progesterone, and prolactin were measured by radioimmunoassay. Commercial kits from Diagnostic Products Corporation for estradiol and progesterone, and an established in-house double antibody assay for prolactin, were utilized. Statistical analysis was performed using ANOVA, followed by Newman-Keuls post hoc test when applicable. Estradiol concentrations were increased throughout gestation from 16.2 ± 6.2 pg/mL (mean ± SD) in the non-pregnant rat to 23.2 ± 8.8, 25.0 ± 7.7, and 30.3 ± 29.6 pg/mL on gestational days 7, 14, and 20, respectively. Progesterone showed the same trend, increasing from 7.2 ± 3.6 ng/mL in the non-pregnant rats to 25.9 ± 4.8, 43.0 ± 8.6, and 47.3 ± 8.8 ng/mL on gestational days 7, 14, and 20, respectively (p<0.05). Prolactin levels were decreased from the non-pregnant state (39.2 ± 22.8 ng/mL) through the early and mid-pregnancy (25.2 ± 20.4, 16.5 ± 16.9 ng/mL, respectively; p<0.05) and rose to pre-pregnancy levels on pregnancy day 20 (39.2 ± 20.4 ng/mL). The effect of pregnancy on serum hormone concentrations in Long-Evans rats were determined and compared to non-pregnant controls. This data may assist in simulating various stages of pregnancy for use in hormonal and receptor binding studies, and in isolating pregnancy hormone effects on the central nervous system in the Long-Evans rat.