title: Inhibition of active K transport in the isolated midgut of Hyalophora cecropia by Tl+.
abstract: The midgut of the American silkworm transports potassium actively from blood side to lumen. The active K transport was measured by short-circuiting the gut. The K transport is inhibited by Tl in the lumen solution. A Lineweaver-burk plot showed that the inhibition with Tl is competitive with the active K transport. The Km was found to be 5.7 +/- 0.7 and Ki = 0.1. It was conclude that Tl acts on the K pump which is located close to the lumen of the gut. When Tl was applied to the blood-side, only about half inhibition is found, yet, paradoxically, Tl concentration in the gut tissue was ten times as high as when Tl was applied to the lumen side.
mesh_terms: D000818:Animals; D001693:Biological Transport, Active / Q000187:drug effects; D012831:Bombyx / Q000187:drug effects / Q000502:physiology*; D004064:Digestive System / Q000187:drug effects / Q000378:metabolism*; D011188:Potassium / Q000378:metabolism*; D013793:Thallium / Q000494:pharmacology*
chemical_list: D013793:Thallium; D011188:Potassium