Tegumental disruption with Triton X-100 and its effects on longitudinal muscle function in male Schistosoma mansoni

Abstract

Longitudinal muscles in adult male Schistosoma mansoni appear to remain in almost all respects functional after tegumental disruption by Triton X-100. Responses to high K+, ouabain, low temperature, praziquantel and neurotransmitters are still present. Muscle membrane potentials remain near those of control animals and lanthanum nitrate is still excluded from the muscle after the Triton treatment. Although muscle contractility remains after tegumental disruption, sodium and calcium levels, as measured by plasma emission spectroscopy, increase by 20-30% while potassium and magnesium levels decrease by 15%. 45Ca2+ accumulation is double that of control animals. Upon exposure to a bathing medium lacking Ca2+, Triton-treated animals lose responsiveness to high K+, ouabain, low temperature and praziquantel more rapidly than do control animals. D-600, which effectively blocks the high K+ response in control animals, has no measurable effect on the high K+ response in Triton-treated animals, suggesting that voltage-dependent Ca2+ channels are present in the tegument.

Praziquantel: physiological evidence for its site(s) of action in magnesium-paralysed Schistosoma mansoni

“…clonazepam (Pax et al 1978(Pax et al , 1983 and these contractions are inhibited by Co 2+ , Ni 2+ , La 3+ , and Cd 2+ . The praziquantel-induced tone is blocked in a non-competitive manner by Mg 2+ but this block is a function of the Mg 2+ : Ca 2+ ratio, making Mg 2+ competitive with extracellular Ca 2+ .…”

“…The parasites were allowed to recover for at least 1 h in the 01 % BSA-RPMI before testing. Detegumentation was confirmed by the inability of the treated parasites to exclude 0-1 % trypan blue and their lack of a tegumental membrane potential and an intact sarcolemmal potential of -25 to -3 0 mV (Depenbusch et al 1983).…”

“…Parasites that have developed flaccid paralysis lose this sensitivity, and this insensitive condition can be overcome by either elevating [Ca 2+ ] in the bath or inclusion of the Ca 2+ ionophore, A-21387, treatments that are expected to increase Ca 2+ flux into the parasite by overcoming or by-passing the plasma membrane barrier. The flaccid paralysis is not due to an alteration in the contractile processes since this Mg 2+ -ATPase activity is not altered in praziquantel-treated schistosome preparations (Pax et al 1983). If the state of flaccid paralysis was due to competition at the sites regulating the contractile elements, an alteration in the permeability of the plasma membranes would still be required to account for the slower recovery of the parasites from flaccid paralysis than the control parasites once they are returned to the control medium.…”

“…mon or similar mechanisms of action are (1) each is dependent on the presence of Ca 2+ in the bath (Wolde Mussie et al 1982;Xiao et al 1984) and (2) each is prevented when the parasites are incubated in a medium containing 30 mM Mg 2+ and 0-4 HIM Ca 2+ (Bricker et al 1983;Pax et al 1978). In this 30 mM Mg 2+ medium, the parasites do contract in response to praziquantel but the contraction is not tonic, rather it is phasic and once the parasites relax they enter a state of flaccid paralysis in which they are not responsive to other stimuli that are expected to cause contraction, such as depolarization with 60 mM K + (Fetterer et al 1980) or exposure to 10 fiM 3-methyl clonazepam (Pax et al 1978(Pax et al , 1983. Schistosomes bathed in the 30 mM Mg 2+ medium and induced to contract with 60 mM K + (Fetterer et al 1980) or 10 fiM 3-methyl clonazepam (Pax et al 1978(Pax et al , 1983 do not enter the state of flaccid paralysis.…”

“…In this 30 mM Mg 2+ medium, the parasites do contract in response to praziquantel but the contraction is not tonic, rather it is phasic and once the parasites relax they enter a state of flaccid paralysis in which they are not responsive to other stimuli that are expected to cause contraction, such as depolarization with 60 mM K + (Fetterer et al 1980) or exposure to 10 fiM 3-methyl clonazepam (Pax et al 1978(Pax et al , 1983. Schistosomes bathed in the 30 mM Mg 2+ medium and induced to contract with 60 mM K + (Fetterer et al 1980) or 10 fiM 3-methyl clonazepam (Pax et al 1978(Pax et al , 1983 do not enter the state of flaccid paralysis. These results demonstrate that in a medium with a higher Mg 2+ : Ca 2+ ratio, praziquantel alters the Ca 2+ flux mechanisms that are involved in muscle contraction and tegumental blebbing of the schistosome in some unique manner, a manner that might give insight into the site and mechanism of action of praziquantel.…”