INSL3 ligand-receptor system in the equine testis.

This research explored the expression and role of INSL3, a hormone like insulin, in the testes of male horses. It found that the hormone is present in all tested states, though its expression varies and it may impact the development and function of the testes.

Research Methodology

• The researchers employed both molecular and immunological techniques to understand the expression of INSL3. This involved examining tissues from prepubertal testis, postpubertal testes with healthy and impaired spermatogenesis (the process of creating sperm), and undescended (cryptorchid) testes from male horses.
• An additional part of their study involved determining the partial cDNA coding sequences of the equine counterpart of the human relaxin/INSL3-receptor, Lgr8.

Localization and Expression of INSL3

• Through in-situ hybridization and immunohistochemistry methods, the researchers pinpointed the position of INSL3-related cells and molecules. They found INSL3 transcripts and the INSL3 ligand localized to Leydig cells in all types of testes investigated.
• Quantitative polymerase chain reaction (qPCR) analysis indicated that INSL3 expression was down-regulated (decreased) in cryptorchid testes and up-regulated (increased) in descended testes.

Western Blot Analysis

• Western blot analysis, another method used to identify and quantify proteins in a sample, was conducted on protein extracts sampled from both adult normal and cryptorchid testes, along with prepubertal testes.
• The result of the Wester Blot revealed a single immunoreactive band at 14.5 kDa, which corresponds to the predicted size of equine proINSL3.
• A densitometric analysis, used for quantifying the results of a Western blot, demonstrated that the expression of proINSL3 was significantly stronger in adult normal testes compared to extracts from cryptorchid or prepubertal testes.

Conclusion & Implications

• The conclusion drawn was that the decreased expression of immunoreactive INSL3 in cryptorchid and prepubertal equine testis is regulated at the transcription level.
• The researchers also identified the presence of transcripts for equine Lgr8 in the testis. This suggests that the testis might be a target for INSL3, hinting at a role for this hormone in the development or function of equine testes.