Carnitine-binding related supressed oxygen uptake by spermatozoa

Area of Science:

• Reproductive biology
• Spermatozoa physiology
• Biochemistry

Background:

• L-carnitine plays a crucial role in sperm metabolism and motility.
• Differences in L-carnitine uptake and function exist between species and sperm sources.
• Accessory sex organs may influence sperm characteristics relevant to carnitine metabolism.

Purpose of the Study:

• To investigate the effect of L-carnitine on oxygen uptake in ejaculated bovine and human spermatozoa.
• To determine the binding capacity of [3H]-L-carnitine in different sperm populations.
• To explore the influence of accessory sex organs on L-carnitine binding to spermatozoa.

Main Methods:

• Measuring oxygen uptake in response to L-carnitine (25 mM) in ejaculated bovine and human spermatozoa, and epididymal spermatozoa.
• Quantifying [3H]-L-carnitine binding to ejaculated bovine, epididymal bovine, and ejaculated human spermatozoa.

Main Results:

• L-carnitine (25 mM) caused an immediate 40% reduction in oxygen uptake in ejaculated bovine spermatozoa.
• No significant reduction in oxygen uptake was observed in ejaculated human spermatozoa or epididymal spermatozoa (bovine and rat).
• [3H]-L-carnitine binding was five times higher in ejaculated bovine spermatozoa compared to epididymal bovine and ejaculated human spermatozoa.

Conclusions:

• Ejaculated bovine spermatozoa exhibit unique susceptibility to L-carnitine-induced inhibition of oxygen uptake.
• Accessory male sex organs appear to secrete a factor that increases L-carnitine binding sites on spermatozoa.
• This factor enhances [3H]-L-carnitine binding and sperm susceptibility to carnitine inhibition, particularly in ejaculated bovine sperm.