Leptin is a hormonal product of the ob gene, which is involved in energy metabolism and reproduction. Expression of leptin and its receptor in reproductive organs suggests that in addition to its endocrine effects, it may have paracrine/autocrine effects on reproduction. Also, the expression of leptin in human and pig spermatozoa and its secretion by these cells suggest a direct role for leptin in sperm physiology. The present study was the first to investigate the presence of the leptin mRNA transcript in Holstein cattle spermatozoa by reverse transcriptase-polymerase chain reaction (RT-PCR) analysis. Total RNA was extracted from different concentrations of ejaculated or epididymal sperm cells and after synthesis of complementary DNA was subjected to PCR amplification. In both ejaculated and epididymal spermatozoa, leptin transcript was amplified with first set of primers. The first amplicon was used for a nested PCR with second set of primers. Intron-spanning primers were located in exons 2 and 3 to rule out the possibility of a DNA contamination. Amplificons of leptin were only detectable when more than 100 million epididymal or ejaculated spermatozoa was used. Presence of leptin mRNA in the bull spermatozoa suggests that leptin might be involved in the physiological processes of bovine spermatozoa, which remain to be further clarified.

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