title: The rate at which human sperm are immobilized and killed by mild acidity.
abstract: OBJECTIVE
  To determine the rate at which mild acidity immobilizes and kills human sperm and to evaluate an acidic microbicide, BufferGel, for sperm immobilization.
  
  
  METHODS
  Controlled in vitro study.
  
  
  METHODS
  An academic research university and hospital andrology lab.
  
  
  METHODS
  Eight volunteer male sperm donors.
  
  
  METHODS
  Semen samples were treated with hydrochloric acid (HCl) or BufferGel.
  
  
  METHODS
  Sperm motility was measured by using a computerized automated semen analyzer and video microscopy. Sperm membrane permeability and intracellular pH were measured by using fluorescent techniques.
  
  
  RESULTS
  In semen acidified with HCl to pH 4.0, sperm were rapidly immobilized (within 1 min) and were irreversibly immobilized (killed) within 10 minutes. The speed of immobilization and of killing were both linearly proportional to hydrogen ion activity over a pH range of 7.5-4.0. Across the same range, the intracellular pH of human sperm equilibrated to within 0.5 pH units of extracellular pH within 1-2 minutes. BufferGel immobilized sperm significantly faster than HCl from pH 4.0-6.0.
  
  
  CONCLUSIONS
  Exposure to mild acidity rapidly acidifies the intracellular pH of human sperm and is rapidly spermicidal. BufferGel accelerates acid immobilization of sperm.
authors.affiliation: Johns Hopkins University, Union Memorial Hospital, and ReProtect LLC, Baltimore, Maryland, USA.
authors.forename: S S
authors.initials: SS
authors.lastname: Olmsted
authors.forename: N H
authors.initials: NH
authors.lastname: Dubin
authors.forename: R A
authors.initials: RA
authors.lastname: Cone
authors.forename: T R
authors.initials: TR
authors.lastname: Moench
mesh_terms: D000143:Acids; D016923:Cell Death; D002463:Cell Membrane Permeability; D006801:Humans; D006851:Hydrochloric Acid / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D008297:Male; D011419:Propidium / Q000493:pharmacokinetics; D013081:Sperm Motility; D013094:Spermatozoa / Q000737:chemistry* / Q000502:physiology*; D013997:Time Factors
chemical_list: D000143:Acids; D011419:Propidium; D006851:Hydrochloric Acid