Determination of serum levels of Equine Chorionic Gonadotrophin (eCG) during mare gestation by Radioimmunoassay (RIA)

Abstract

The objective is to cuantitate levels of equine chorionic gonadotropin (eCG) along the pregnancy of mare employing a radioimmunoassay technique (RIA) developed with highly specific antibodies. Five race mares were chosen, three years old with pregnancies confirmed by echography. Blood samples were collected from venipuncture of the neck vein at weekly intervals between 0 (estrous) and 120 days and monthly afterwards until parturition. Blood samples from empty mares as well as males were collected followinf the same procedure. A polyclonal antibody raised in rabbits highly specific for eCG was used for the radioimmunoassay. ECG labelled with ¹²⁵l was produced by limiting chloramine-T method with 60±17% yield. Callibration curves with minimum detectable doses of 8.4±2.5 ng/mL, slopes of 0.9±0.3 and dose equivalent of 50% binding (ED^50%) of 100±32 ng/mL. Serum levels of eCG in male as well as empty mare were 148±88 ng/mL. Pregnant mares eCG blood levels increased from the day 35 reaching a maximum at 50 days and reaching ground levels at approximately 150 days. In conclusion a highly sensitive and specific procedure is described for the determination of serum levels of eCG along the mare's pregnancy.