Objective: To determine the rate at which mild acidity immobilizes and kill
s human sperm and to evaluate an acidic microbicide, BufferGel, for sperm i
mmobilization.
Design: Controlled in vitro study.
Setting: An academic research university and hospital andrology lab.
Patient(s): Eight volunteer male sperm donors.
Intervention(s): Semen samples were treated with hydrochloric acid (HCl) or
BufferGel.
Main Outcome Measure(s): Sperm motility was measured by using a computerize
d automated semen analyzer and video microscopy. Sperm membrane permeabilit
y and intracellular pH were measured by using fluorescent techniques.
Result(s): In semen acidified with HCl to ptr 4.0, sperm were rapidly immob
ilized (within 1 min) and were irreversibly immobilized (killed) within 10
minutes. The speed of immobilization and of killing were both linearly prop
ortional to hydrogen ion activity over a pH range of 7.5-4.0. Across the sa
me 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.
Conclusion(s): Exposure to mild acidity rapidly acidifies the intracellular
pH of human sperm and is rapidly spermicidal. BufferGel accelerates acid i
mmobilization of sperm.