title: The mitochondria of stallion spermatozoa are more sensitive than the plasmalemma to osmotic-induced stress: role of c-Jun N-terminal kinase (JNK) pathway.
abstract: Cryopreservation introduces extreme temperature and osmolality changes that  impart lethal and sublethal effects on spermatozoa. Additionally, there is  evidence that the osmotic stress induced by cryopreservation causes oxidative  stress to spermatozoa. The main sources of reactive oxygen species in  mammalian sperm are the mitochondria. In view of this, the aim of our study  was to test whether or not osmotic stress was able to induce mitochondrial  damage and to explore the osmotic tolerance of the mitochondria of stallion  spermatozoa. Ejaculates from 7 stallions were subjected to osmolalities  ranging from 75 to 1500 mOsm/kg, and the effect on sperm membrane integrity  and mitochondrial membrane potential was studied. Additionally, the effects of  changes in osmolality from hyposmotic to isosmotic and from hyperosmotic to  isosmotic solutions were studied (osmotic excursions). The cellular volume of  stallion spermatozoa under isosmotic conditions was 20.4 ± 0.33  μm(3). When exposed to low osmolality, the stallion spermatozoa  behaved like a linear osmometer, whereas exposure to high osmolalities up to  900 mOsm/kg resulted in decreased sperm volume. Although sperm membranes were  relatively resistant to changes in osmolality, mitochondrial membrane  potential decreased when osmolalities were low or very high (10.7 ±  1.74 and 16.5 ± 1.70 at 75 and 150 mOsm/kg, respectively, and 13.1  ± 1.83 at 1500 mOsm/kg), whereas in isosmolar controls the percentage  of stallion sperm mitochondria with a high membrane potential was 41.1  ± 1.69 (P < .01). Osmotic excursions induced greater damage  than exposure of spermatozoa to a given nonphysiologic osmolality, and again  the mitochondria were more prone to damage induced by osmotic excursions than  was the sperm plasma membrane. In search of intracellular components that  could mediate these changes, we have detected for the first time the c-Jun  N-terminal kinase 1/2 in stallion spermatozoa, which are apparently involved  in the regulation of the viability of these cells.
authors: Veterinary Teaching Hospital, Laboratory of Equine Reproduction, Faculty of Veterinary Medicine, University of Extremadura, Avd. de la Universidad s/n, Cáceres, Spain.
authors: Beatriz Macías
authors: BM
authors: García
authors: Alvaro Miró
authors: AM
authors: Moran
authors: Lauro González
authors: LG
authors: Fernández
authors: Cristina Ortega
authors: CO
authors: Ferrusola
authors: Antolin Morillo
authors: AM
authors: Rodriguez
authors: Juan Maria Gallardo
authors: JM
authors: Bolaños
authors: Carolina Maria Balao
authors: CM
authors: da Silva
authors: Heriberto Rodríguez
authors: HR
authors: Martínez
authors: Jose A
authors: JA
authors: Tapia
authors: Fernando J
authors: FJ
authors: Peña
mesh_terms: D000818:Animals; D005434:Flow Cytometry; D006736:Horses; D048031:JNK Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D008297:Male; D008564:Membrane Potentials; D009995:Osmosis; D013094:Spermatozoa / Q000648:ultrastructure*; D013312:Stress, Physiological
chemical_list: D048031:JNK Mitogen-Activated Protein Kinases