Effects of glutamine, proline, histidine and betaine on post-thaw motilityof stallion spermatozoa

The supplementation of the freezing diluent with 3 amino acids (glutamine, proline and histidine) and 1 amino acid-related compound (betaine) in prese rving stallion spermatozoa diluted in INRA82 extender containing 2.5 % (v/v ) glycerol and 2% (v/v) egg yolk (control extender) during freezing and tha wing was studied at 0, 40, 80, 120 and 160 mM in 20 split ejaculates (10 st allions x 2 ejaculates; Experiment 1). Glutamine and:proline were studied a t 0, 10, 20, 30, 40, 50, 60, 70 and 80 mM in 20 split ejaculates (10 stalli ons x 2 ejaculates; Experiment 2). In each experiment, spermatozoa were eva luated after thawing: by computer automated sperm analyzer. The percentage of motile spermatozoa (faster than 30 mu m/sec) was assessed. In addition, the velocity of the average path (VAP), the straight line velocity (VSL), t he curvilinear velocity (VCL) and the amplitude of the lateral head displac ement (ALH) were also measured. In Experiment 1, only glutamine (40 mM) significantly improved sperm motili ty (56.0% +/- 3.0 vs: 49.7% +/- 1.6 ; P<0.05) compared with the control ext ender, while velocities were unaffected at concentrations of 40 to 120 mM. However, at 160 mM, a significant decrease in motility and:velocity was obs erved for all amino acids. In Experiment 2, motility in glutamine (range 41 .1% +/- 3.8; 42.4% +/- 3.6) and proline (43.0% +/- 3.7; 35.6% +/- 3.8). ext enders compared with the control (34.7% +/-: 1.6) was improved significantl y (P<0.05). Sperm velocity was improved at concentrations higher than 40 mM glutamine and 50 mM proline. (C) 1999 by Elsevier Science Inc.