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Journal of Experimental Biology 143,87-100 (1989)
Published by Company of Biologists 1989

AMINO ACID TRANSPORT SYSTEMS IN BRUSH-BORDER MEMBRANE VESICLES FROM LEPIDOPTERAN ENTEROCYTES

GIORGIO M. HANOZET 1, BARBARA GIORDANA 1, V. FRANCA SACCHI 2, and PAOLO PARENTI 1

1 Dipartimento di Fisiologia e Biochimica Generali, Universitd di Milano, Via Celoria 26, 20133 Milano, Italy
2 Istituto di Fisiologia Generale e Chimica Biologica, Universita di Milano, Via Saldini 50, 20133 Milano, Italy

The presence of different potassium-dependent amino acid transport systems in the luminal membrane of the larval midgut of Philosamia cynthia Drury (Saturnidae, Lepidoptera) was investigated by means of countertransport experiments performed with brush-border membrane vesicles. The vesicles were preloaded with 14 different unlabelled amino acids, whose ability to elicit an intravesicular accumulation over the equilibrium value of six labelled amino acids (L-alanine, L-leucine, L-phenylalanine, L-glutamic acid, L-lysine and L-histidine) was tested. For histidine, the results were compared with those obtained from inhibition experiments, in which the same 14 amino acids were used as inhibitors on the cis side of the brush-border membrane. The data demonstrate the presence in the lepidopteran luminal membrane of distinct transport pathways for lysine and glutamic acid. The transport of most neutral amino acids, with the exclusionof glycine and proline, seems to occur through a system that may be similar to the neutral brush-border system (NBB) found in mammalian intestinal membranes. This system is also able to handle histidine.

Key words: counterflow accumulation, inhibition, amino acid transport systems, brush-border embrane vesicles, lepidopteran larvae midgut

Accepted on January 4, 1989






© The Company of Biologists Ltd 1989