QUICK SEARCH:   [advanced] Author: Keyword(s):
Home     Help     Feedback     Subscriptions     Archive     Search     Table of Contents

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by MURDOCK, L. L. Articles by KOIDL, B. Search for Related Content PubMed Articles by MURDOCK, L. L. Articles by KOIDL, B.

Journal of Experimental Biology 56,795-808 (1972)
Published by Company of Biologists 1972

Blood Metabolites After Intestinal Absorption of Amino Acids in Locusts

L. L. MURDOCK ¹ and B. KOIDL ¹

¹ Fachbereich Biologie, Universitat Konstanz, 775 Konstanz, West Germany

1. After infusion of the locust gut with L-glutamate-U-¹⁴C, L-glutamine was found to be the major radioactive product in blood sampled 1 h later. Smaller amounts of alanine were also found. In most experiments not even traces of unchanged L-glutamate were detectable.

2. When D-glutamate was infused, the main radioactive product was D-glutamate, with lesser amounts of glutamine. With L-alanine-1-¹⁴C, the major product was unchanged alanine, with smaller amounts of glutamine. With glycine-1-¹⁴C, only glycine could be recovered.

3. Gastric caeca, which presumably are the major tissue sites of amino acid absorption, metabolized L-glutamate to glutamine and alanine. Metabolism of glycine was negligible.

4. Slow infusion of L-glutamate-1-¹⁴C into the haemocoel of locusts was followed by recovery of the radioactivity from blood as glutamine. Unchanged L-glutamate was not in evidence.

5. Rises in the blood concentration of L-glutamate appear to be suppressed. This seems not to be the case for D-glutamate, L-alanine, and glycine.

6. Destruction of dietary L-glutamate in the gut wall may be a functional adaptation to help maintain a low blood concentration of the pharmacologically active substance while producing energy required for absorption and tissue maintenance. Should any L-glutamate enter the blood from the gut or other tissue source, it will be converted to glutamine, which suggests the existence of a complementary mechanism for ensuring low blood L-glutamate.