Effect of bovine serum albumin concentration and source on sperm capacitation in the golden hamster.

Since virtually all experiments on sperm capacitation routinely include serum albumin in the culture media, the relative effect of BSA concentration on sperm capacitation was investigated. The fertile life of hamster sperm, as measured by the ability to penetrate the zona pellucida, decreased from 5 to 3 h as the concentration of BSA was increased from 3 to 18 mg/ml. To determine the extent of sperm capacitation in sperm populations that resulted in 100% penetration, the rate and timing of sperm penetration through the zona pellucida was determined. For each insemination, the rate of sperm penetration (%/min), the time when 50% of the eggs were zona-penetrated (T50), and the sperm capacitation index (T50/rate) were calculated. The extent of sperm capacitation as measured by all three parameters increased as the duration of preincubation or the BSA concentration was increased. The data on the duration of preincubation and the BSA concentration matrix indicated two properties of the effect of BSA on sperm capacitation: 1) the extent of sperm capacitation after the first hour of preincubation was independent of BSA concentration; and 2) when sperm were preincubated for two or more hours, the capacitating effectiveness of BSA was saturable; the saturating concentration of BSA decreased as the duration of preincubation increased. To determine whether the first hour of preincubation is independent of BSA, sperm were preincubated for 1 h without BSA and then 2 h with BSA. The extent of sperm capacitation of these sperm was equal to that of the 3-h control sperm; thus the first hour of capacitation is independent of BSA.(ABSTRACT TRUNCATED AT 250 WORDS)