Dose-dependent effects of prolactin on biological and receptor responses in Toxocara cati larvae in vitro.

Toxocara cati is an important zoonotic nematode and a contributor to human toxocariasis, with predominantly transmammary transmission in cats. Although prolactin has been shown to influence the biology and vertical transmission of T. canis, its direct effects on T. cati larvae have not previously been investigated. The present study evaluated the in vitro effects of prolactin on the growth, motility, viability, and prolactin receptor-like (PRL-R-like) immunoreactivity of T. cati larvae. Embryonated eggs were obtained from molecularly confirmed female T. cati worms collected from stray cats in Ahvaz, Iran. Viable larvae were cultured in RPMI-1640 medium and exposed to prolactin concentrations of 0, 2, 20, 40, and 400 ng/mL for 20 days. Larval growth, motility, and viability were assessed at intervals, while PRL-R-like immunoreactivity was evaluated immunocytochemically at the end of incubation. Prolactin increased larval growth in a dose- and time-dependent manner, with the strongest effect observed at 20 ng/mL (P < 0.01). Moderate prolactin concentrations (20-40 ng/mL) improved larval survival, whereas 400 ng/mL was associated with reduced viability and motility. Immunocytochemical analysis demonstrated increased PRL-R-like immunoreactivity in prolactin-treated larvae, particularly at 20-400 ng/mL, with the strongest signal at 40 and 400 ng/mL (P < 0.001). Motility changes were not statistically significant. These findings provide the first evidence that T. cati larvae exhibit prolactin-associated biological responses, suggesting that hormonal signals may contribute to larval activation, persistence, and transmammary transmission. The study highlights the potential role of endocrine regulation in the biology and transmission dynamics of feline toxocariasis.