Work

Tryptophan promotes sperm hyperactivation in hamsters via 5-hydroxytryptamine biosynthesis within sperm

Year: 2025

Type: article

Abstract: L-tryptophan (Trp), an essential amino acid, is a precursor of 5-hydroxytryptamine (5-HT; also known as serotonin) that promotes mammalian sperm hyperactivation. Since mammalian sperm contain Trp hydroxylase (TPH), they may contribute to 5‑HT biosynthesis. Therefore, this study aimed to examine the effect of Trp on hamster sperm hyperactivation and determine whether sperm are involved in 5-HT biosynthesis. Trp significantly enhanced sperm hyperactivation via the 5-HT4 receptor and its associated signals. In contrast, D-tryptophan did not affect sperm hyperactivation. Furthermore, hamster sperm contained the 5-HT biosynthesis enzymes TPH and aromatic L-amino acid decarboxylase (AADC). Additionally, hamster sperm secreted 5-HT. Trp-enhanced hyperactivation and 5-HT secretion were significantly inhibited by TPH and AADC inhibitors. Overall, our findings suggest that Trp enhanced sperm hyperactivation through the biosynthesis of 5-HT within the sperm.

Source: Journal of Reproduction and Development

DOI: 10.1262/jrd.2025-006

Authors: Issei SUZUKI, Masakatsu FUJINOKI, Takao KAMAI

Institution: Dokkyo Medical University

Language: English

Topic: Sperm and Testicular Function

Subfield: Reproductive Medicine

Field: Medicine

Domain: Health Sciences

Open Access status: gold

Estimated APC paid: $828

Funders: Dokkyo Medical University, Japan Society for the Promotion of Science