Purification and characterization of donkey chorionic gonadotrophin.

The research study focuses on isolating and identifying the properties of chamionic gonadotrophin from pregnant donkeys (dCG). Unlike the gonadotrophin from pregnant mares (eCG), dCG showed itself to be primarily an LH or luteinizing hormone in biological tests. Despite similarities with eCG, there were noticeable differences in its composition.

Isolation of dCG

• The discovery of donkey chorionic gonadotrophin (dCG) in pregnant donkey serum was isolated using similar methods previously used for pregnant mare chorionic gonadotrophin (eCG).
• Upon detection and isolation, it was determined that the donkey’s chorionic gonadotrophin predominantly behaves as a luteinizing hormone (LH) in various biological tests.

Comparative Research

• The research compares the potency of dCG and eCG in a series of tests. Both hormones were found to be similarly active in in-vitro rat Leydig cell assays. However, dCG was considerably less potent than eCG in the in-vitro rat seminiferous tubule assay for Follicle-stimulating hormone (FSH) and in the augmentation assay. Moreover, dCG was noted to be at least nine times more potent in LH than in FSH activity.

Composition Analysis

• The dCG was found to have fewer carbohydrates (31%) compared to eCG (45%). There were also distinct differences in their amino acid compositions.
• A single amino-terminal residue, phenylalanine, was observed in dCG reinforcing its unique characteristic.

Immunological Reactions

• In immunological terms, dCG cross-reacted in homologous radio-immunoassays for eCG, equine LH and equine FSH. However, the inhibition curves were nonparallel with those of the respective equine gonadotrophin standards, indicating different immunological property.