Serum and Seminal Plasma Zinc Levels and Immunopositivity of the ZIP6 and ZIP14 Transporters in Men with Normo- and Teratozoospermia

Abstract

Zinc plays a crucial role in spermatogenesis, sperm function, and fertilisation. Zinc homeostasis is regulated by ZIP and ZnT transporter proteins, which mediate Zn2+ influx and efflux across sperm cell membranes. This study analysed total Zn concentration in seminal plasma and serum of 10 normozoospermic and 32 teratozoospermic men involved in the process of infertility treatment, using inductively coupled plasma mass spectrometry. In addition, the expression of Zn transporters ZIP6 and ZIP14 in the sperm of two normozoospermic and two teratozoospermic men was analysed using immunofluorescence. Applying Student’s t test and the Mann–Whitney U test, we found no significant differences in Zn concentrations in seminal plasma and serum between groups. ZIP6 was mainly localised in the sperm head, with slightly higher immunopositivity in normozoospermic than teratozoospermic samples, but there was no statistically significant difference between the groups. ZIP14 was mainly found in the sperm head, and some teratozoospermic samples showed immunopositivity in the tail, although there were no significant differences in ZIP14 immunopositivity between normozoospermic and teratozoospermic samples. The results suggest that Zn concentrations in seminal plasma and serum, and the expression of ZIP6 and ZIP14, do not differ in normo- and teratozospermic samples, and emphasise the complex interplay of factors underlying male fertility.