Na-Uptake by the Larval Midgut of the Cecropia Silkworm

Abstract

Lepidopteran larvae have high potassium/low sodium concentrations in blood, tissue, and gut content. Their amino acid uptake in the midgut is by a potassium amino acid cotransporter, in which potassium can be substituted by sodium. Sodium uptake has been suggested to depend upon amino acid uptake. The present study shows that sodium can be taken up independently of amino acids with a flux ratio of about 100. The potential difference across the midgut is favorable for sodium uptake, but can only account for about 50% of the uptake.