Fig. 2. Phosphorylation of glycogen synthase kinase 3 (GSK3) isoforms in human spermatozoa with different motility. (A) Representative western blot of GSK3 in human spermatozoa with different motility conditions. (B) Sperm motility of 40% was used as the criterion for normal motility according to the World Health Organization lower reference limit of human sperm motility. The ratio of p-GSK3α(Ser21)/GSK3α was positively correlated with human sperm motility. No significant difference in the ratio of p-GSK3α(Tyr279)/GSK3α, p-GSK3β(Tyr216)/GSK3β, p-GSK3α/β(Ser21/9)/GSK3α/β, and p-GSK3α/β(Tyr279/216)/GSK3α/β was found between the high-motility spermatozoa and low-motility spermatozoa. AU: arbitrary units, ND: not detected. ^*Significantly different from low-motility spermatozoa by Mann–Whitney U-test at p<0.05 levels. X and circles indicate mean and individual values, respectively.