ATP-INDUCED CHANGES IN [Ca2+]i IN SPERMATOZOA OF INFERTILE MEN WITH OLIGO- AND ASTHENOZOOSPERMIA

Abstract

Calcium is the major second messenger which plays an important role in sperm physiology. A decreased fertility potential of spermatozoa is closely associated with the disturbances of Ca²-homeostasis. ATP is present in the female reproductive tract and may play an important role in the fertilization process. Since intracellular calcium ([Ca²⁺]_i) is the main determinant of many physiological processes occurring in sperm, we set out to describe the Ca²⁺-signals in response to extracellular ATP (ATP_e) in spermatozoa of fertile (normozoospermia) and infertile men (oligo- and asthenozoospermia). ATP_e-induced changes in [Ca²⁺]_i in spermatozoa were studied using 2 mM fluorescent probe Fluo-4. ATP_e caused a rapid transient elevation in [Ca²⁺]_i. We found that kinetics and magnitude of the [Ca²⁺]_i changes induced by the ATP_e were different in normo- and pathospermic cells. Specifically, the average value of peak amplitudes of [Ca²⁺]_i rise induced by 5 mM ATP_e in oligozoospermic samples was not significantly different from the normozoospermic samples. In the asthenozoospermic samples, the ATP_e-induced peak amplitude of [Ca²⁺]_i changes was in 1.5 fold lower (P<0.05) compared to that in the normozoospermic samples. ATP_e-induced increase in [Ca²⁺]_i in sperm cell has a concentration-dependent manner in both normozoospermic and pathozoospermic  samples. In the oligozoospermic samples, the [Ca²⁺]_i transient response was 2.5 fold (P<0.05) slower than in the normozoospermic samples. Differences in ATP_e-induced [Ca²⁺]_i transients between astheno- and normozoospermic samples were also significant (P<0.05) although less pronounced. The obtained results clearly demonstrate ATP_e-induced increase in [Ca²⁺]_i transients are disturbed in pathozoospermic samples which may be detrimental to sperm activation and may result in fertilization failure or abnormality. Taken into account the importance reproductive techniques, specifically for in vitro fertilization and intrauterine insemination present study suggest that modu­lation of [Ca²⁺]_i signals and sperm function by the ATP_e may be beneficial for artificial reproductive techniques used in reproductive biology and medicine.