A modified transmembrane migration method for evaluating the spermicidal potency of some nonoxynol compounds

Abstract

The transmembrane migration technique, a simple method in-vitro for quantitatively assessing the effects of a drug on human sperm motility, has been evaluated. The original method has been modified to include a preincubation step, and the incubation time has been reduced to 90 min. In semen samples possessing sperm concentrations of less than 75 x 12(6) spermatozoa mL-1 the volume of the lower reservoir has been reduced to 1 mL. This modified method has been used to compare the spermicidal potency of the widely employed non-ionic surfactant nonoxynol-9, with nonoxynol-5 and nonoxynol-15 (containing, respectively, fewer and more ethylene oxide units per molecule). The rank order of spermicidal potency of the compounds evaluated was nonoxynol-9 = nonoxynol-5 greater than nonoxynol-15.

PIP: A modified transmembrane migration method was used to evaluate the spermicidal potency of nonoxynol-9 and to make comparisons with 2 other water-soluble nonoxynols -- nonoxynol-5 and nonoxynol-15. The proportion of sperm which moves across the membrane from the upper to the lower chamber was assessed and expressed as the transmembrane migration ratio (TMR). Semen samples were collected by masturbation after at least 3 days' sexual abstinence, from a pool of 8 healthy volunteers (18-35 years). The characteristics noted of each sample included spermatozoa concentration and sperm motility, the percentage dead sperm being assessed using ethidium bromide, and fluorescence microscopy. The rank order of potency of the nonoxynols examined was nonoxynol-5=nonoxynol 9, which was greater than nonoxynol-15. The varying potency of the nonoxynols with respect to their IC50 values corresponds to the pertinent lipophilic nature of each compound. An observed increase in the IC50 was related to an increase in the side-chain lengths: 5915. This relationship indicates the importance of lipophilicity in the properties of these surfactants to diffuse into the sperm plasma membrane and disturb its conformation and semipermeable nature, preventing the occurrence of both sperm motility and ovum fertilization.