Calcitonin gene-related peptide regulates amino acid absorption across ratjejunum

The calcitonin gene related peptide (CGRP) is widely distributed in the ent eric nervous system and gut afferents. Its role in normal digestion and abs orption is not characterised. This study is conducted to elucidate whether CGRP regulates amino acid absorption in the small intestine. In in vivo exp eriments using the single-pass perfusion technique, intravenous infusion of CGRP (250-750 pmol/kg-min) reduced alanine absorption by 35-40%. The effec ts were completely blocked by the antagonist hCGRP (8-37). Moreover, intrav enous infusion of CGRP antagonist blocked the inhibitory effect of intralum inal capsaicin perfusion on alanine absorption. Similarly, intracerebral in jection of CGRP decreased alanine absorption, an effect which was reduced b y vagotomy. In vitro experiments using isolated jejunal strips showed that CGRP reduced alanine absorption in a dose-dependent manner. At 6 pM, CGRP d ecreased alanine absorption by 33%. Similarly, CGRP reduced the absorption of proline and taurine by 20 and 11.5%, respectively. Kinetic studies revea led that CGRP reduces alanine influx into intestinal epithelial cells by in hibiting the affinity of the carriers. It is demonstrated that CGRP is invo lved in the regulation of jejunal amino acid absorption through intrinsic ( enteric) and extrinsic (central) neural mechanisms. (C) 2000 Elsevier Scien ce B.V. All rights reserved.