Microelectrode studies of the tegument and sub-tegumental compartments of male Schistosoma mansoni: anatomical location of sources of electrical potentials

Abstract

Histological studies using horse-radish peroxidase (HRP) as a marker, injected iontophoretically through a recording electrode, have indicated the origins of potentials encountered upon advancement of the electrode into and beneath the dorsal surface of adult male Schistosoma mansoni. The first potential encountered, having a value of -51 +/- 0.6 mV originates across the outer tegumental membrane. The next potential has a value of -28 +/- 0.6 mV and originates in the muscle masses underlying the tegument. Finally, a potential having the value -10 +/- 0.5 mV originates within the basal lamina and the interstitial fibers and extracellular space surrounding the muscle. Altering ion concentrations in the bathing medium (i.e. high K+, low Na+, zero Ca2+, low Cl-, high Li+) depolarizes all three potentials. External applications of ouabain and the antischistosomal, praziquantel, also cause depolarization of the potentials. It appears that the muscle potential and the tegumental potential are primarily K+-dependent. The depolarizing effects of ouabain. LiCl and low Na+ suggest that active transport is important in the maintenance of the muscle potential, just as is the case for the tegumental potential. There appears to be a close correlation between changes in the tegumental, muscle and extracellular space potentials. The correlation between tegument and muscle potential changes might be explained by junctional complexes between tegumental cell bodies and muscle cell bodies.