Viability, acrosome morphology and fertilizing capacity of boar spermatozoa treated with strontium chloride

• Published in: Zygote (Cambridge) Vol. 16; no. 1; p. 49
• Main Authors: Okada, Konosuke, Palmieri, Chiara, Della Salda, Leonardo, Vackova, Irena
• Format: Journal Article
• Language: English
• Published: England 01-02-2008
• Subjects: Acrosome - physiology; Acrosome Reaction - drug effects; Acrosome Reaction - physiology; Animals; Cell Survival - drug effects; Fertilization in Vitro; Male; Microinjections; Oocytes - physiology; Sperm Motility - drug effects; Sperm Motility - physiology; Sperm-Ovum Interactions - drug effects; Spermatozoa - physiology; Strontium - pharmacology; Sus scrofa; Swine
• ISSN: 0967-1994
• DOI: 10.1017/S0967199407004479

The positive effect of strontium ions (Sr2+) on sperm motility, capacitation and acrosome reaction has been demonstrated in the mouse, human, guinea pig and hamster. In the present study, we have evaluated the effect of Sr2+ on the viability and acrosome morphology of boar spermatozoa, and on the fertilization and development after the microinjection of Sr(2+)-treated spermatozoa into porcine oocytes. Before incubation, 79% of spermatozoa were classified as propidium iodide (PI)-negative (live) using the LIVE/DEAD Sperm Viability Kit. After incubation with strontium chloride (SrCl2), 39% (0 mM; no divalent cations), 25% (1.9 mM) and 24% (7.5 mM) of them were classified as PI-negative. The proportion of spermatozoa that had initiated the acrosome reaction was higher in Sr(2+)-containing medium than in Sr(2+)-free medium, when assessed by electron microscopy. There was no significant difference in percentage of spermatozoa initiating the acrosome reaction between Sr2+-treated groups (1.9 mM: 22%, 7.5 mM: 33%, p>0.05). After the microinjection of spermatozoa incubated with SrCl2, 67% (1.9 mM) and 61% (7.5 mM) of injected oocytes were successfully fertilized, and then 43% (1.9 mM) and 41% (7.5 mM) contained a fully decondensed sperm head. Sham-injected oocytes were significantly activated at a lower rate than Sr(2+)-treated groups (27%, p<0.05). Next, after microinjection of spermatozoa incubated with 1.9 mM SrCl2 (n=51), 45% of injected oocytes cleaved on day 2, and 18% developed to blastocysts on day 7 (sham-injection, n=48: 15% to cleavage and 0% to blastocyst). These results demonstrate that Sr2+ is likely to positively affect the fertilizing capacity of spermatozoa in the pig.