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 T1 in the lumen solution. A Lineweaver-Burk plot showed that the inhibition with T1 is competitive with the active K transport. The Km was found to be 5·7 ± 0·7 and Ki = 0·1. It was concluded that T1 acts on the K pump which is located close to the lumen of the gut. When T1 was applied to the blood-side, only about half inhibition is found, yet, paradoxically, T1 concentration in the gut tissue was ten times as high as when T1 was applied to the lumen side.

© 1982 by Company of Biologists
1982
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