Schistosoma mansoni: measurement of Na+ ion activity in the tegument and the extracellular spaces using ion-selective microelectrodes.
Ion-selective microelectrodes were used to measure sodium ion activity (aNa) in the tegument and interstitial spaces in adult male Schistosoma mansoni. In RPMI 1640, aNa averaged 31 +/- 13 mM in the tegument, a value significantly less than that in the bathing medium. In the interstitial spaces, it averaged 72 +/- 17 mM, a value nearly the same as that in the bathing medium. In hypo- or hyperosmotic media, aNa in the interstitial spaces varied by a value commensurate with change in aNa in the medium, but aNa in the tegument was changed by only a small amount. Monensin (10 microM), low temperature (20 C), and ouabain (0.3 to 10 microM) all caused significant increases in aNa in the tegument. Hypo- and hyperosmotic media produced initial weight changes followed by gradual recovery back toward original weights. It is concluded that the schistosome is a volume regulating osmoconformer with osmolality of the extracellular fluid approximating that of the bathing medium, but that within the tegument of the parasite, Na+ concentration is controlled by active transport processes.
D000818:Animals; D004594:Electrophysiology; D005110:Extracellular Space / Q000502:physiology; D008297:Male; D008839:Microelectrodes; D008985:Monensin / Q000494:pharmacology; D010042:Ouabain / Q000494:pharmacology; D012550:Schistosoma mansoni / Q000502:physiology*; D012964:Sodium / Q000502:physiology*; D013696:Temperature; D014882:Water-Electrolyte Balance
D010042:Ouabain; D008985:Monensin; D012964:Sodium