Functional attenuation of human sperm by novel, non-surfactant spermicides: precise targeting of membrane physiology without affecting structure.
BACKGROUND
We have attempted to identify structural, physiological and other targets on human sperm vulnerable to the spermicidal action of two novel series of non-detergent molecules, reported to irreversibly immobilize human sperm in <30 s, apparently without disrupting plasma membrane.


METHODS
Three sperm samples were studied. Scanning and transmission electron microscopy were used to assess structural aberrations of sperm membrane; plasma membrane potential and intracellular pH measurements (fluorometric) were used to detect changes in sperm physiology; reactive oxygen species (ROS, fluorometric) and superoxide dismutase activity (colorimetric) were indicators of oxidative stress; and sperm dynein ATPase activity demonstrated alterations in motor energy potential, in response to spermicide treatment. Post-ejaculation tyrosine phosphorylation of human sperm proteins (immunoblotting) was a marker for functional integrity.


RESULTS
Disulfide esters of carbothioic acid (DSE compounds) caused complete sperm attenuation at > or =0.002% concentration with hyper-polarization of sperm membrane potential (P < 0.001), intracellular alkalinization (P < 0.01), ROS generation (P < 0.05) and no apparent effect on sperm (n = 150) membrane structure. Isoxazolecarbaldehyde compounds required > or =0.03% for spermicidal action and caused disrupted outer acrosomal membrane structure, depolarization of membrane potential (P < 0.001), intracellular acidification (P < 0.01) and ROS generation (P < 0.01). Detergent [nonoxynol-9 (N-9)] action was sustainable at > or =0.05% and involved complete breakdown of structural and physiological membrane integrity with ROS generation (P < 0.001). All spermicides caused functional attenuation of sperm without inhibiting motor energetics. Unlike N-9, DSE-37 (vaginal dose, 200 microg) completely inhibited pregnancy in rats and vaginal epithelium was unchanged (24 h,10 mg).


CONCLUSIONS
The study reveals a unique mechanism of action for DSE spermicides. DSE-37 holds promise as a safe vaginal contraceptive. CDRI Communication No. 7545.
Jain
Rajeev K
RK
Division of Endocrinology, Central Drug Research Institute (CSIR), Lucknow 226 001, India.
Jain
Ashish
A
Kumar
Rajeev
R
Verma
Vikas
V
Maikhuri
Jagdamba P
JP
Sharma
Vishnu L
VL
Mitra
Kalyan
K
Batra
Sanjay
S
Gupta
Gopal
G
D000282:Administration, Intravaginal; D000818:Animals; D004220:Disulfides / Q000008:administration & dosage / Q000494:pharmacology; D004398:Dyneins / Q000378:metabolism; D005260:Female; D006801:Humans; D006863:Hydrogen-Ion Concentration; D066298:In Vitro Techniques; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects; D008855:Microscopy, Electron, Scanning; D046529:Microscopy, Electron, Transmission; D017137:Nonoxynol / Q000008:administration & dosage / Q000494:pharmacology; D018384:Oxidative Stress / Q000187:drug effects; D011247:Pregnancy; D051381:Rats; D017382:Reactive Oxygen Species / Q000378:metabolism; D013081:Sperm Motility / Q000187:drug effects; D013089:Spermatocidal Agents / Q000008:administration & dosage / Q000494:pharmacology*; D013094:Spermatozoa / Q000187:drug effects* / Q000502:physiology* / Q000648:ultrastructure; D013482:Superoxide Dismutase / Q000378:metabolism
C519274:DSE-37 compound; D004220:Disulfides; D017382:Reactive Oxygen Species; D013089:Spermatocidal Agents; D017137:Nonoxynol; D013482:Superoxide Dismutase; D004398:Dyneins