Priming procedure and hormone preparations influence rat granulosa cell response

Area of Science:

• Endocrinology
• Reproductive Biology
• Biochemistry

Background:

• Follicle-stimulating hormone (FSH) and luteinizing hormone (LH) are critical reproductive hormones.
• Equine (e) and ovine (o) gonadotropins, including equine FSH (eFSH), equine LH (eLH), equine chorionic gonadotropin (eCG), and ovine LH (oLH), exhibit distinct biological activities.
• Understanding their specific activities is crucial for reproductive research and applications.

Purpose of the Study:

• To compare the FSH activity of equine gonadotropins (eFSH, eLH, eCG) and ovine LH (oLH) using multiple assay methods.
• To evaluate the influence of different granulosa cell priming conditions (diethylstilbestrol [DES] vs. eCG) on hormone activity.
• To highlight the impact of assay methodology and reference standards on interpreting gonadotropin function.

Main Methods:

• Utilized a FSH radioreceptor assay with rat testicular homogenate.
• Assessed plasminogen activator production in granulosa cells from DES- or eCG-primed rats.
• Measured steroidogenic activity (progesterone production) in granulosa cells from DES- or eCG-primed rats.

Main Results:

• Ovine LH showed minimal FSH activity across all assays.
• Equine FSH demonstrated the highest activity in receptor binding and cellular assays, with variations depending on cell priming.
• Equine LH and eCG exhibited minimal activity in DES-primed cells but showed activity in eCG-primed cells, though with non-parallel dose-response curves compared to eFSH.

Conclusions:

• Equine LH and eCG activity is dependent on granulosa cell priming, being inactive in DES-primed cells but active in eCG-primed cells.
• Assay conditions and the choice of reference standards significantly impact the comparative assessment of gonadotropin activity.
• Equine gonadotropins serve as a key example illustrating how different assay systems can yield divergent conclusions about hormone function.