Equine inhibin/activin beta A-subunit mRNA is expressed in the endometrial gland, but not in the trophoblast, during pregnancy.

The research studied the expression of inhibin and activin proteins in equine pregnancy and found that activin, but not inhibin, is predominantly produced in the endometrial glands of the pregnant mare.

Research Methodology

• The study explored the presence of two proteins – inhibin alpha- and inhibin/activin beta A-subunit mRNA – in equine uteroplacental tissues during various stages of pregnancy – from days 90 to 300.
• Northern blot analysis was used to probe for the presence of these proteins. This analytical tool allows scientists to detect specific RNA (ribonucleic acid) molecules among a mixture of RNA.
• In addition, in situ hybridization was conducted to identify the tissue localization of beta A-subunit mRNA. This technique involves using a labelled complementary strand of DNA or RNA to localize a specific DNA or RNA sequence in a tissue.

Research Findings

• Results from the Northern blot analysis showed that five transcripts of beta A-subunit were present. The most frequently expressed transcript was the 1.5 kb.
• Interestingly, relatively high levels of the 1.5 kb transcript were seen in the second trimester of pregnancy compared to the third trimester.
• In situ hybridization revealed presence of the beta A-subunit mRNA specifically in the endometrial glands, but not in the fetal placental tissue, also known as trophoblast, at days 150, 210, and 300 of pregnancy.
• The inhibin alpha-subunit transcript, on the other hand, could not be detected at any stage of pregnancy through either the Northern blot analysis or in situ hybridization.

Conclusions and Implications

• Based on the findings of this study, it was concluded that activin, but not inhibin, is predominantly produced in the endometrial glands of the pregnant mare.
• The team postulates that this produced activin may play a significant role at a paracrine or endocrine level during pregnancy in horses. A paracrine action is one where a substance has an effect only in the immediate vicinity of the cell that released it whereas endocrine action is when a hormone is released into the bloodstream and travels to act on target cells at a distance.
• The factors regulating the gene expression of the beta A-subunit in equine tissue remains unknown and possibly forms the basis for further research in this field.