Year: 2010
Type: dissertation
Abstract: The effect of the chemoattractant bourgeonal on [Ca\\(^{2+}\\)]i and chemotaxis in human sperm was investigated. Burgeonal induced a dose-dependent, slowly-developing tonic elevation in [Ca\\(^{2+}\\)]i, The response was dependent on capacitation. In low-Ca\\(^{2+}\\) or EGTA-buffered saline the response to bourgeonal was inhibited. Pretreating spermatozoa with bis-phenol (20μM) to release stored Ca\\(^{2+}\\) did not alter the response. Thus bourgeonal acts primarily by inducing Ca\\(^{2+}\\) influx. Treatment of sperm with bourgeonal caused an increase in [cAMP]. When cells were pretreted with bourgeonal in low-Ca\\(^{2+}\\)saline, subsequent introduction of Ca\\(^{2+}\\) resulted in a single, large [Ca\\(^{2+}\\)]i transient in >75% of the cells, indicating that sudden influx of Ca\\(^{2+}\\) caused closure of the bourgeonal-sensitive Ca\\(^{2+}\\)- channel. This negative feedback was not modulated by IBMX (1mM) or dbcAMP (1mM), indicating that cAMP was not involved and that a direct action Ca\\(^{2+}\\) was more likely. Both Ni\\(^{2+}\\) (10μM) and La\\(^{3+}\\) (100μM) inhibited the action of bourgeonal on [Ca\\(^{2+}\\)]i, suggesting a possible role of CNG channels. Exposing sperm to a temporal bourgeonal gradient caused a series of transient [Ca\\(^{2+}\\)]i elevations in >20% of the cells. A gradient of progesterone (another characterised chemoattractant for human sperm) induced similar Ca\\(^{2+}\\) 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 [Ca\\(^{2+}\\)]o but was unaltered by TMB-8 (an inhibitor of stored Ca\\(^{2+}\\) store release), thus showing a dependence on Ca\\(^{2+}\\) influx similar to the [Ca\\(^{2+}\\)]i signal.
Authors: M. Concepción García García, Auden Andres
Language: English
Subfield: Reproductive Medicine
Field: Medicine
Domain: Health Sciences
Open Access status: green
OpenAlex ID: W141159168