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The rate at which human sperm are immobilized and killed by mild acidity
S S Olmsted1, N H Dubin, R A Cone
1Johns Hopkins University, Union Memorial Hospital, and ReProtect LLC, Baltimore, Maryland, USA.
Objective:
To determine the rate at which mild acidity immobilizes and kills human sperm and to evaluate an acidic microbicide, BufferGel, for sperm immobilization.
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 computerized automated semen analyzer and video microscopy. Sperm membrane permeability and intracellular pH were measured by using fluorescent techniques.
Result(S):
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.
Conclusion(S):
Exposure to mild acidity rapidly acidifies the intracellular pH of human sperm and is rapidly spermicidal. BufferGel accelerates acid immobilization of sperm.
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