Permeation and Membrane Transport in Animal Parasites: Amino Acid Permeation into Tapeworms from Elasmobranchs

Abstract

A study was made of the kinetics of permeation of L-valine-C14 and L-leucine-C14 into the tapeworm, Calliobothrium verticillatum, from the smooth dogfish. The kinetics are those to be expected in a catalytic process. The dissociation constant for L-valine permeation at 10[degree] C is about 2 x 10-3 and for L-leucine about 1 x 10-3. Heat of activation for L-valine permeation is about 9000 calories/mole. Either L-valine or L-leucine competitively inhibits permeation of the other. Certain other amino acids inhibit permeation of the test amino acids. Permeation of L-leucine is inhibited by previous incubation of worms in iodoacetate or dinitrophenol. Addition of glucose does not affect permeation of L-valine or L-leucine, but permeation of L-leucine is affected by pH, maximum permeation occurring at 7.4.