Plasma Luteinizing Hormone, Follicle-Stimulating Hormone and Prolactin During Pregnancy in the Mouse¹

Abstract

Concentrations of LH, FSH and prolactin (PRL) were measured by radioimmunoassay throughout pregnancy (day of vaginal plug = day 0) in mice exposed to light for 14 hr (on between 0500–1900 hr). During the preimplantation period an increase in LH occurs, with a peak on day 3. Another peak appears during midpregnancy, with the greatest level of LH appearing on day 10 (37 ± 12 ng/ml). A comparable level was found only on the day of parturition. Levels of FSH were greatest on day 0 and on the day of parturition. FSH concentrations were low (<600 ng/ml) before implantation; after implantation the levels fluctuated between 550–900 ng/ml. Prolactin levels were low on day 0, fluctuated between 161–304 ng/ml from day 1 through 7, and reached their highest level on day 8 (396 ± 28 ng/ml). Levels then decreased to less than 130 ng/ml on days 9 through 16, rose on days 17 and 18, but decreased again on the day of parturition.Placental extracts were also assayed using the RIA for pituitary gonadotropins. Only a PRL-like hormone was detected in the extracts, but this may be accounted for by the presence of blood trapped within the placentae. The patterns of circulating gonadotropins in the pregnant mouse are found to differ radically at times from what has been reported for the pregnant rat. (Endocrinology94: 112, 1974)