RESUMEN
Little or no motility is observed when sperm from 5 mammalian species are incubated in vitro in their cauda epididymal fluid (CEF). We examined the effects of pH, lactate, and viscoelastic drag on sperm motility to determine whether these factors are responsible for this inhibition of motility. The pHs of CEF from bull, dog, rat, guinea pig, and hamster were 5.8, 6.2, 6.9, 6.9, and 7.2, respectively. The lactate concentration of epididymal semen collected from anesthetized animals ranged from 0.6 to 0.9, but increased almost 10-fold in samples from rats or dogs when measured 2 h postmortem. Increasing the pH of CEF to 7.0 resulted in the initiation of full motility for bull and dog sperm. Suspensions of sperm in buffer at various pHs (from 4.0 to 7.6) produced a sigmoidal motility curve for all species. All species, including bull and dog, showed almost full motility in buffer at a pH equal to the pH of their own CEF. Motility of bull and dog sperm showed greater inhibition with decreasing pH when suspended in CEF instead of buffer. The addition of 15 mM lactate, which has been shown to lower sperm intracellular pH, shifted the motility versus pH curves of all species toward higher pH. In bull and dog the addition of lactate produced a motility profile that was indistinguishable from that in their own CEF. The viscoelastic drag of the CEF of only two species, rat and hamster, was sufficiently high to inhibit sperm motility. We conclude that the low pH of the CEF from bulls and dogs plus the presence of lactate is sufficient to cause inhibition of motility.(ABSTRACT TRUNCATED AT 250 WORDS)
Asunto(s)
Equilibrio Ácido-Base/efectos de los fármacos , Lactatos/farmacología , Motilidad Espermática/efectos de los fármacos , Animales , Bovinos , Cricetinae , Perros , Epidídimo/efectos de los fármacos , Cobayas , Concentración de Iones de Hidrógeno , Lactatos/metabolismo , Ácido Láctico , Masculino , Ratas , Especificidad de la Especie , ViscosidadRESUMEN
Immobilin, the highly viscoelastic glycoprotein isolated from rat cauda epididymal fluid, exhibits all of the key biochemical characteristics of a mucin: 1) it has a very high molecular weight (will not pass through a 10(6) dalton cut-off filter; 2) it contains 56% carbohydrate, with low or undetectable levels of mannose, xylose and uronic acid; 3) the carbohydrates (primarily galactose, N-acetylglucosamine and N-acetylgalactosamine) are arranged in short, oligosaccharide chains (4-20 monosaccharides per chain); 4) these oligosaccharide chains can be cleaved by NaOH in the presence of NaBH4, suggesting O-glycosidic linkages; and 5) the protein core is pronase-resistant. Immobilin, however, contains no detectable sialic acid, and 67% of the oligosaccharides are uncharged, indicating that immobilin is less acidic than most other mucins.
Asunto(s)
Epidídimo/análisis , Glicoproteínas/aislamiento & purificación , Moco/análisis , Animales , Líquidos Corporales/análisis , Centrifugación por Gradiente de Densidad , Fenómenos Químicos , Química , Cromatografía por Intercambio Iónico , Elasticidad , Glicoproteínas/fisiología , Péptidos y Proteínas de Señalización Intercelular , Masculino , Oligosacáridos/análisis , Ratas , Ratas Endogámicas , ViscosidadRESUMEN
In many mammals, sperm are immotile while stored in the caudal epididymis and do not become motile until ejaculation. We report here our investigation of the mechanism that initiates motility in mature rat epididymal sperm. We found that an external "activator" is not required to initiate rat sperm motility since immotile sperm started to swim immediately when exposed to solutions that contributed only osmotic support. Instead, we found that epididymal rat sperm are kept fully immobilized by a high molecular weight glycoprotein, "immobilin," that we have isolated from rat cauda epididymal (CE) fluid. Our results strongly support the hypothesis that immobilin inhibits sperm motility mechanically simply by creating a highly viscoelastic environment: 1) rat CE fluid inhibited the motility of such disparate cells as rat sperm, E. coli. and rabbit sperm (which are fully motile in rabbit CE fluid), 2) the degree to which a variety of enzymatic treatments or slight dilution of the CE fluid initiated sperm motility depended only on the degree to which the treatment reduced the viscoelastic drag of the fluid, and 3) centrifugation of CE fluid simultaneously copurified the component of the fluid that immobilizes the sperm, the component that renders the fluid viscoelastic, and the glycoprotein immobilin.