ACTIONS OF SPERMICIDAL AND VIRUCIDAL AGENTS ON ELECTROGENIC ION TRANSFER ACROSS HUMAN VAGINAL EPITHELIUM IN-VITRO

Human ectocervical tissue was removed at operation over the menstrual cycle mounted as a sheet in vitro in an Ussing-style chamber and incub ated in bicarbonate saline. The net electrogenic ion transport was mea sured as the short-circuit current (Isc in mu amps/cm(2)) and was char acterised as mainly (60-86%) an amiloride-sensitive electrogenic Na+ t ransport (lumen to serosa). Serosal application of amiloride had no ef fect. Serosal application of ouabain, a selective Na+-pump inhibitor, reduced the Isc to near zero but neither theophylline (10 mM) nor furo semide (1 mM) had any action. The data are compatible with a model ect ocervical vaginal cell having an amiloride-sensitive Na+ entry mechani sm at the lumenal membrane and a Na+-pump at the basolateral membrane removing the ion from the cell. The effects of the putative virucides, chlorhexidine and benzalkonium chloride, were tested oil the preparat ion. Mucosally added chlorhexidine (2 mg/ml) had no effect on the Isc or tissue resistance bur benzalkonium chloride, at concentrations betw een 0.06-1.2%, caused a rapid fall in the Isc. At the highest concentr ation this was only partly reversible even after two washes with fresh buffer. At the lowest concentration (0.03%) benzalkonium chloride som etimes caused an initial increase in the Isc which then fell to zero. In all the tissues even after the Ise was reduced to near zero, nigros in left in contact with the tissue for 5 min. did not enter and stain the cells, indicating the detergent had a selective membrane action ra ther than causing a non-specific increase in permeability. The prepara tion allows objective measurements to be made of the initial acute mem brane actions of putative spermicides and virucides on human vaginal e ctocervical epithelial cells and offers a new approach of assessing th eir pharmacological/toxicological actions.