Sperm membrane potential

Zeng, Y., Clark, E.N., and Florman, H.M. (1995). Sperm membrane potential Hyperpolarization during capacitation regulates zona pellucida dependent acrosomal secretion. Dev. Biol. 777 554-,563. 

Receptor stimulation by ZP3 leads to the activation of several primary signal transducers including the heterotrimeric, GTP-binding regulatory proteins, or G proteins, a cation channel that regulates sperm membrane potential, and a tyrosine kinase activity. These pathways will be considered separately and then crosstalk between these signaling mechanisms will be discussed. 

This cation channel is activated at an early step in ZP3 signal transduction, as indicated in pharmacological studies (Florman, 1994 Arnoult et al., 1996a). Channel activation produces a small ( 50 nM), transient (1-2 min duration) elevation of Ca i that is restricted to the sperm head. However, this modest rise is not sufficient to initiate acrosome reactions (Florman, 1994). A more plausible role for this channel is to control sperm membrane potential (V ) during ZP3 signal transduction. 

Espinosa, F. and Darszon, A. (1995). Mouse sperm membrane potential Changes induced by Ca . FEBSLett. 572 119-125. 

The acrosomal process of some invertebrate sperm cells is an actin cable that sometimes forms almost instantaneously by polymerization of the actin monomers and shoots out to penetrate the outer layers of the egg during fertilization (Chapter 32). The stereocilia, the "hairs" of the hair cells in the inner ear, contain bundles of actin filaments.302 Motion of the stereocilia caused by sound produces changes in the membrane potential of the cells initiating a nerve impulse. In certain lizards each hair cell contains about 75 stereocilia of lengths up to 30 pm and diameter 0.8 pm and containing more than 3000 actin filaments in a semicrystalline array. Microvilli (Fig. 1-6) contain longitudinal arrays of actin filaments. 

Schackmann, R.W., Christen, R., and Shapiro, B.M. (1981). Membrane potential depolarization and increased intracellular pH accompany the acrosome reaction of sea urchin sperm. Proc. Natl. Acad. Sci. 78 6066-6070. 

Beltran C, Zapata O, Darszon A. 1996. Membrane potential regulates sea urchin sperm adenylylcyclase. Biochemistry 35 7591-7598. 

Self-referencing ion-selective electrodes have seen attractive applications in a diversity of medical problems. For example, the vacuolar-type H+-ATPase has been shown to play an important role in the acidification of the lumen of the proximal vas deferens, part of the male reproductive system. An acidic luminal fluid is required for the maintenance of sperm quiescence and for the prevention of premature activation of acrosomal enzymes during their storage in the epididymis and vas deferens. Proton secretion in the proximal vas deferens has been measured with the self-referencing technique (Fig. 6) [40]. Likewise, altered potassium homeostasis is indicative of dying cells, as the transplasma membrane potential is no longer maintained, as measured in both viable and nonviable embryos [41]. 

Troiano, L. Granata, A. R. M. Cossarizza, A. Kalashnikova, G. Bianchi, R. Pini, G. Tropea, F. Carani, C. Franceschi, C. Mitochondrial membrane potential and DNA stainability in human sperm cells a flow cytometry analysis with implications for male infertility. Exp. Cell Res. 1998, 241, 384-393. 

Chou, K. Chen, J. Yuan, S. X. Haug, A. The membrane potential changes polarity during capacitation of murine epididymal sperm. Biochem. Biophys. Res. Commm. 1989,165, 58-64. 

Taurine (2-aminoethanesulfonic acid 4.235) is an inhibitory neurochemical that probably acts primarily as a neuromodulator rather than a neurotransmitter. It is formed from cysteine, and its accumulation can be prevented by the cardiac glycoside ouabain. Although receptor sites and specific actions cannot be elucidated without an antagonist, taurine has been implicated in epilepsy and, potentially, in heart disease. There are a large number of physiological effects attributed to taurine, among them cardiovascular (antiarrythmic), central (anticonvulsant, excitability modulation), muscle (membrane stabilizer), and reproductive (sperm motility factor) activity. Analogs of taurine, phthalimino-taurinamide (4.236) and its iV-alkyl derivatives, are less polar than taurine and are potent anticonvulsant molecules. 

Microtubules occur in a single row below the plasma membrane of spermatozoa, although their distribution varies in different species (171). In H. diminuta and the Cyclophyllidea (Fig. 7.2), in general, they completely encircle the spermatozoon (171,212,835), often exhibiting helical periodicity. In Phyllobothrium gracile (Fig. 1.2(b)) the cortical microtubules may be confined to two demi-circles, lateral or external to the axonemes (561,564). The significance of these different distributions of microtubules in relation to potential sperm activity is not known. 

Primakoff, P., Hyatt, H., and Tredick-Kline, J. (1987). Identification and purification of a sperm surface protein with a potential role in sperm-egg membrane fusion. J. Cell Biol. 704 141-149. 

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