THE ROLE OF NITRIC-OXIDE IN REPRODUCTION

Nitrix oxide (NO) is a highly reactive and short-lived radical (half-I ife time: 10-12 s), which is derived from L-arginine by the NO synthas es (NOS) in several organ systems. The release of NO by endothelial ce lls leads to rapid relaxation of vascular smooth muscle cells, whereas release by several neuronal cells causes neurotransmission. When NOS is actively Induced in immune cells or certain epithelia it causes cyt otoxicity and/or apoptosis of these cells. In the reproductive organs NO is now considered to be an important trigger molecule for several p hysiological mechanisms. Follicular synthesized NO is involved in rupt ure of the follicle during ovulation. Moreover, NO participates in the acrosome reaction of spermatozoa during capacitation. Apoptosis and c ollagenolysis of the functional endometrium may be involved in endomet rial shedding during menstruation. Since NO induces both apoptosis and collagenolysis, the newly discovered production of NO in late secreta ry endometrium could act as a key mechanism in the process of menstrua l disintegration of the endometrium. Additionally, NO is necessary to support and maintain the decidualization process and plays a pivotal r ole in implantation.