title: Improvement and Evaluation of a Staining Method for Measuring Sperm Lactate Dehydrogenase C4 Activity.
abstract: BACKGROUND
  This study sought to improve and evaluate a 2-hydroxyvaleric acid based staining method for detection of lactate dehydrogenase C4 (LDH-C4) activity in human spermatozoa.
  
  
  METHODS
  A staining method for measuring sperm LDH-C4 activity with the substrate 2-hydroxyvaleric acid was improved. Expression level of LDH-C4 was assessed by Western blotting. The diagnostic performance was evaluated by plotting the receiver operating characteristic (ROC) curve.
  
  
  RESULTS
  The positive products were black purple lumps concentrated in the neck segment of spermatozoa. Expression level of LDH-C4 was significantly reduced in the low activity infertile cases as compared to the matched contrasts. Decreased LDH-C4 level was significantly correlated with the declined enzyme activity (r = 0.702, p = 0.000). The ROC curve allowed for the discrimination between low and normal LDH-C4 activity cases with a sensitivity of 0.912 and specificity of 0.895, corresponding to an area under curve (AUC) of 0.941.
  
  
  CONCLUSIONS
  The improved method hallmarks a promising accuracy in evaluating sperm LDH-C4 activity. Down-regulated LDH-C4 level is a culprit for the decreased LDH-C4 activity in spermatozoa.
authors.forename: Zhaolei
authors.initials: Z
authors.lastname: Cui
authors.forename: Cuihua
authors.initials: C
authors.lastname: Fan
authors.forename: Chunxiu
authors.initials: C
authors.lastname: Pang
authors.forename: Dezhu
authors.initials: D
authors.lastname: Zheng
authors.forename: Yaohua
authors.initials: Y
authors.lastname: Liu
authors.forename: Liangyuan
authors.initials: L
authors.lastname: Chen
authors.forename: Duo
authors.initials: D
authors.lastname: Zhang
authors.forename: Fenghua
authors.initials: F
authors.lastname: Lan
mesh_terms: D000328:Adult; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007527:Isoenzymes / Q000378:metabolism; D007770:L-Lactate Dehydrogenase / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D012372:ROC Curve; D013094:Spermatozoa / Q000201:enzymology*; D013194:Staining and Labeling / Q000379:methods*; D013696:Temperature
chemical_list: D007527:Isoenzymes; D007770:L-Lactate Dehydrogenase; C409673:lactate dehydrogenase C4