STUDIES ON THE PERMEABILITY TO WATER, SODIUM, AND CHLORIDE OF THE HYDATID CYST OF ECHINOCOCCUS GRANULOSUS

The permeability to water, sodium, and chloride of Echinococcus granulosus hydatid cysts obtained from secondarily infected mice was determined in vitro under steady-state conditions. Water diffused rapidly across the cyst membranes (diffusional permeability 1.88 X 10-' cm sec'-) and this rate increased after preincubation of cysts with antidiuretic hormone. Permeability to sodium and chloride was relatively low (0.13 and 0.035 A/moles hr'- cm-2, respectively) as compared with other epithelial membranes. In addition to new insight into host-parasite relationships, studies of cyst permeability could provide an approach to the development of a rational chemotherapy for hydatid disease. Knowledge of permeability characteristics may be provided by the characterization of barriers and mechanisms for the translocation of ions and molecules into the cyst. The fact that cer- tain substances can be detected in the cyst fluid has relatively little value if detection re- quires weeks or months of exposure. Quantita- tive data on permeability of specific substances would help to elucidate structure-activity re- lationships and to better define the time neces- sary to reach effective concentrations inside the cyst of potential cysticidal and protoscoli- cidal drugs. Studies in this direction were championed by Schwabe and co-workers (1959, 1961) who followed the changes of the weight of hydatid daughter cysts incubated in solutions of electrolytes and nonelectrolytes and obtained information on the permeability of the wall. A quantitative approach depends on the availability of suitable methods to mea- sure unidirectional fluxes, rate constants, and permeabilities under controlled experimental conditions. In the present work we discuss the choice of a suitable methodology and report some experimental findings.