Key Points

• Capacitation is associated with a mild oxidative stress. The generation of ROS (O2'- and NOO, by spermatozoa themselves, is essential and occurs as an early step of capacitation.

• O2" and NO^ are synthesized by sperm enzymes, oxidase and NOS, and these ROS appear to have specific targets. Exogenous addition of ROS, combined with the use of inhibitors and ROS scavengers, gives important indications on cellular processes involved but does not replace actual measurements of endogenously formed ROS.

• The oxidase is likely at the membrane level since O2" is released extracellularly. There may be more than one NOS, one being stimulated at the beginning of capacitation and another being part of the signal transduction cascades related to this process.

• Spermatozoa are at the present time the only cell type in which a reciprocal (double sided) ROS-induced ROS formation is demonstrated, O2'- promoting NO' synthesis and vice versa.

• Sg is a natural regulator for ROS generators, both the oxidase and NOS.

• Zn2+ is also a major physiological regulator of ROS generation, but is also expected to directly regulate some of the enzymes (e.g., PKC) involved in signal transduction cascades.

• The SH/SS couple is involved both as regulator of ROS formation and target for ROS action.

• Both O2'- and NO' promote the signal transduction pathways known to be involved during capacitation and as a consequence also the late protein Tyr phosphorylation that occurs downstream of all these. ROS may act via oxidation of protein SH to activate or inhibit several enzymes (kinases, phosphatases, etc.) of these cascades.

• Sperm hyperactivation and acrosome reaction are also modulated by ROS. ROS may then be acting on other targets since these events are differently controlled.

' Sperm activation is characterized by stimulation of several processes, multiplicity of enzymatic pathways and types of regulation, cross talks, apparent redundancy of mechanisms, etc. This is expected to insure that spermatozoa acquire their fertility potential.

Pregnancy Guide

Pregnancy Guide

A Beginner's Guide to Healthy Pregnancy. If you suspect, or know, that you are pregnant, we ho pe you have already visited your doctor. Presuming that you have confirmed your suspicions and that this is your first child, or that you wish to take better care of yourself d uring pregnancy than you did during your other pregnancies; you have come to the right place.

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