Genetic and temporal variation in serum concentrations and biological activity of horse chorionic gonadotrophin.

The study examines the varying levels of chorionic gonadotrophin (CG), a hormone crucial to pregnancy, and its associated activities in rodent bioassay systems. Factors influencing these variations include the genetics of the parent horses and the gestation period. The researchers found that the levels of the hormone could potentially be increased by choosing specific sire and mare pairs, and the biological activity of the hormone changes during the gestation period due to differences in its carbohydrate content.

Investigation into the Variation in CG Levels

• The research studied the different quantity levels of chorionic gonadotrophin (CG), a hormone key to initiating pregnancy, within rodents within bioassay systems. This hormone carries out its functions through two associated hormonal activities – follicle-stimulating hormones (FSH) and luteinizing hormones (LH).
• The findings revealed that a portion of the variability in CG could be attributed to the male horse (stallion) that sired the pregnancy. This suggests that stallion genetics have an influence on CG production.

Temporal Variation and Genetic Influence on Hormonal Activities

• The study found that FSH activity per unit of CG was found to be greater at Days 71 and 104 of the gestation period than at Day 39. This suggests that the FSH activity linked with CG alters as the pregnancy progresses.
• Similarly, LH activity per unit of CG was found to vary depending on the sire involved with the pregnancy. However, contrary to FSH activity, no effect of the gestation day could be demonstrated on LH activity.

Proposed Function of Carbohydrate Content in CG Variations

• The research demonstrated that the removal of a specific type of sugars called sialic acid increased the bioactivity of LH. This suggests that changes in the carbohydrate content of CG might be a factor causing the variation in its biological activity.
• Thus, the study proposes that the variations in biological activity among animals and during the gestation period might be influenced by differences in carbohydrate content of CG. This concept also contributes to the understanding of how CG’s effectiveness changes according to genetics and pregnancy timelines.