Tl+ permeates the Hyalophora cecropia midgut equally in both directions, but the flux of Tl+ per mm is up to 50 times higher than the passive flux for potassium, rubidium and caesium. This is explained by assuming that the Tl+ flux is a carrier-mediated facilitated diffusion or a passage through channels similar to gramicidin channels in black membranes. We have found this special way for Tl+ to pass through membranes in the Hyalophora cecropia midgut; some other membranes, such as red blood cells, seem to show the same properties, but others, such as frog muscle and skin, do not.

This content is only available via PDF.