Tris buffer improves fluorescence yield of ram spermatozoa when evaluating membrane integrity.

Area of Science:

• Animal Reproduction
• Sperm Biology
• Fluorescence Microscopy

Background:

• Assessing ram sperm membrane integrity is vital for reproductive success.
• Fluorochromes like propidium iodide (PI) and CFDA are commonly used but buffer effects are not fully understood.

Purpose of the Study:

• To evaluate the impact of different buffer solutions on fluorescence signal intensity for PI and CFDA in ram sperm.
• To determine the optimal buffer for accurate membrane integrity assessment.

Main Methods:

• Ram sperm ejaculates were diluted in various buffers (MOPS, TRIS, TES, HEPES, citrate, phosphate).
• Membrane integrity was assessed using PI and CFDA staining within 24 hours of storage at 15°C.
• Mean fluorescence intensity (FI), fluorescence background noise (FBN), and fluorescence contrast (FC) were quantified using Image J software.

Main Results:

• TRIS diluent resulted in significantly higher FI and FC for both PI- and CFDA-labeled sperm compared to other buffers.
• Citrate and phosphate buffers showed intermediate FC for PI-labeled sperm but lower FC for CFDA-labeled sperm due to increased FBN.
• TRIS buffer limited fluorescent labeling to sperm heads, unlike other buffers where tails were also labeled.

Conclusions:

• TRIS buffer markedly increases the fluorescence yield of PI/CFDA-labeled ram sperm.
• Buffer selection significantly influences fluorescence-based membrane integrity assessment in ram sperm.
• TRIS buffer is recommended for enhanced fluorescence signal in ram sperm viability testing.