Prolactin affects bovine oocytes through direct and cumulus-mediated pathways

Area of Science:

• Reproductive Biology
• Endocrinology
• Cell Signaling

Background:

• Prolactin (PRL) is implicated in mammalian oocyte maturation.
• Understanding PRL's specific action pathways in bovine oocytes is crucial for reproductive research.

Purpose of the Study:

• To characterize PRL action pathways in bovine oocytes.
• To investigate PRL receptor presence, effects on meiosis resumption, and developmental capacity.

Main Methods:

• Detected PRL receptor mRNA and protein in oocytes and cumulus cells via RT-PCR and immunocytochemistry.
• Assessed meiosis resumption in cumulus-oocyte complexes (COCs) and denuded oocytes (DOs) with or without PRL and pathway inhibitors.
• Evaluated embryo development post-in vitro maturation (IVM), in vitro fertilization (IVF), and in vitro culture (IVC).

Main Results:

• PRL receptor mRNA and protein were present in both oocytes and cumulus cells.
• PRL retarded meiosis resumption in DOs (but not COCs) independently of gonadotropins, involving tyrosine kinases and NO synthase.
• PRL increased blastocyst yield in COCs when combined with gonadotropins, indicating a role for cumulus cells.

Conclusions:

• Demonstrated a direct PRL signaling pathway in bovine oocytes via receptor expression.
• Identified a direct meiosis-retarding effect of PRL involving tyrosine kinases and NO synthase.
• Established that PRL enhances oocyte developmental capacity through cumulus cells expressing PRL receptors.