The response of human spermatozoa to chemoattractants

The effect of the chemoattractant bourgeonal on [Ca²⁺]i and chemotaxis in human sperm was investigated. Burgeonal induced a dose-dependent, slowly-developing tonic elevation in [Ca²⁺]i, The response was dependent on capacitation. In low-Ca²⁺ or EGTA-buffered saline the response to bourgeonal was inhibited. Pretreating spermatozoa with bis-phenol (20μM) to release stored Ca²⁺ did not alter the response. Thus bourgeonal acts primarily by inducing Ca²⁺ influx. Treatment of sperm with bourgeonal caused an increase in [cAMP]. When cells were pretreted with bourgeonal in low-Ca²⁺saline, subsequent introduction of Ca²⁺ resulted in a single, large [Ca²⁺]i transient in >75% of the cells, indicating that sudden influx of Ca²⁺ caused closure of the bourgeonal-sensitive Ca²⁺- channel. This negative feedback was not modulated by IBMX (1mM) or dbcAMP (1mM), indicating that cAMP was not involved and that a direct action Ca²⁺ was more likely. Both Ni²⁺ (10μM) and La³⁺ (100μM) inhibited the action of bourgeonal on [Ca²⁺]i, suggesting a possible role of CNG channels. Exposing sperm to a temporal bourgeonal gradient caused a series of transient [Ca²⁺]i elevations in >20% of the cells. A gradient of progesterone (another characterised chemoattractant for human sperm) induced similar Ca²⁺ oscillations (in >20% of the cells), which increased in amplitude and frequency in response to the increasing progesterone concentration. Human spermatozoa responded chemotactically to a 1nM bourgeonal gradient, Chemotaxis was dependent on capacitation. The response was inhibited in low [Ca²⁺]o but was unaltered by TMB-8 (an inhibitor of stored Ca²⁺ store release), thus showing a dependence on Ca²⁺ influx similar to the [Ca²⁺]i signal.

Name dc:type.qualificationname

d_ph

Level dc:type.qualificationlevel

d_ph

Grantor dc:publisher.institution

University of Birmingham

Year dc:date.issued

2010

Author dc:creator

• Morales Garcia, Auden Andres

• QH301 Biology