Nitric Oxide and Superoxide Anion Production During Heparin-Induced Capacitation in Cryopreserved Bovine Spermatozoa.

The aim of this work was to quantify NO, O and ONOO production during heparin-induced capacitation of cryopreserved bovine spermatozoa. A time dependent hyperbolic increase was observed for heparin-dependent capacitation, O uptake, and NO production. Conversely, O production was increased during the first 15 min of incubation, showing a decrease from this time until 45 min. At 15 min of heparin incubation, a threefold increase in O consumption (5.9 ± 0.6 nmol/min × 10 cells), an enhancement in NO release (1.1 ± 0.2 nmol/min × 10 cells), and a five-fold increase in O production (1.3 ± 0.07 nmol/min × 10 cells), were observed. Peroxynitrite production rate was estimated taking into account NO and O generation and the second-order rate constant of the reaction between these species. To conclude, heparin-induced capacitation of cryopreserved bovine spermatozoa activates (i) mitochondrial O uptake by high ADP levels due to increased energy requirements, (ii) NO production by a constitutive NOS and (iii) O production by a membrane-bound NAD(P)H oxidase. The products of both enzymes are released to the extracellular space and could be involved in the process of sperm capacitation. [ABSTRACT FROM AUTHOR]