ROSInduced ROS

The close relation between O2'- and NO' synthesis rises the possibility of an ROS-induced ROS formation as occurs in other cell types. As examples, NO2 generation increases in cultured glial cells treated with xanthine+xanthine oxidase, an effect abolished by SOD [72] and, conversely, H2O2 stimulates NOS in porcine aortic endothelial cells via a complex signaling pathway [57].

Several observations confirm the hypothesis of an ROS-induced ROS system operating during sperm capacitation [46] . The first indication is that SOD blocks capacitation due to l-Arg (NOS substrate) and NO' itself (from DA-NONOate) and that the NOS inhibitor l-NMMA prevents that due to O2'- (from xanthine + xanthine oxidase) (Fig. 4.4a) [46]. Second is that endogenous NO' synthesis stops in the presence of SOD (Figs. 4.1c and 4.4b) and conversely that O2'- formation is arrested by NOS inhibitors (Fig. 4.4c) [46]. Additionally, spermatozoa treated with DA-NONOate initiate the synthesis O.'- (Fig. 4.4c) and, conversely, spermatozoa treated with O.'- (from xanthine+xanthine oxidase) produce more NO' , an effect blocked in the presence of SOD (Fig. 4.4b) [46]; it should be stressed here that the amounts of ROS (O2'- and NO') then generated are of the same magnitude as those measured in spermatozoa incubated with FCSu or l-Arg [46]. Moreover, H2O2 promotes synthesis of NO' but not of O2'- suggesting that there is no self-induction of the oxidase [46]. Finally, ONOO- has no effect on either O.'- or NO' generation pointing out that this ROS is a final product rather than initiating agent [46].

Pooling of all these data points out to spermatozoa as the first known cells with a reciprocal (two sided) ROS-induced ROS system, O2'- inducing NO' production and vice versa.

Delicious Diabetic Recipes

Delicious Diabetic Recipes

This brilliant guide will teach you how to cook all those delicious recipes for people who have diabetes.

Get My Free Ebook

Post a comment