Persistence of altered 5-hydroxytryptamine turnover following hemibody X-irradiation in the rat distal colon.
OBJECTIVE
Acute gastrointestinal responses to ionizing radiation exposure include a role for 5-hydroxytryptamine (5-HT), but it is not known whether involvement of 5-HT persists and contributes to late effects. The aim was to investigate the acute and later effects of lower hemibody irradiation on 5-HT turnover and the biological effect in the rat distal colon.


METHODS
Rats were exposed to 10 Gy lower hemibody X-radiation. 5-HT and 5-hydroxyindole acetic acid tissue levels were measured in the distal colon along with the serotonin re-uptake transporter and tryptophan hydroxylase mRNA. 5-HT-containing cells and crypt cell numbers were estimated in addition to 5-HT-stimulated short-circuit current responses in isolated mucosa. Studies were performed from 3 days to 3 months post-exposure.


RESULTS
During the acute phase, at 3 days post-irradiation, reductions in cell number, tissue resistance, serotonin re-uptake transporter expression and secretory responses to 5-HT were observed. However, at later times when secretory responses were normal, 5-HT tissue levels and enterochromaffin cell numbers were increased.


CONCLUSIONS
The results provide evidence that after 10 Gy hemibody irradiation, modifications persist past the acute phase. In particular, 5-HT turnover in the distal colon is altered during a longer period.
Ropenga
A
A
Institut de Radioprotection et de Sûreté Nucléaire, Direction de Radioprotection de l'Homme, Service de Radiobiologie et d'Epidémiologie, IRSN, BP no. 17, F-92262 Fontenay-aux-Roses Cedex, France.
Combes
O
O
Chapel
A
A
Griffiths
N M
NM
D000818:Animals; D001483:Base Sequence; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism; D002455:Cell Division / Q000528:radiation effects; D003106:Colon / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology / Q000528:radiation effects*; D004247:DNA / Q000235:genetics; D004759:Enterochromaffin Cells / Q000378:metabolism / Q000473:pathology / Q000528:radiation effects; D005071:Evoked Potentials / Q000187:drug effects / Q000528:radiation effects; D015870:Gene Expression / Q000528:radiation effects; D006897:Hydroxyindoleacetic Acid / Q000097:blood / Q000378:metabolism; D007413:Intestinal Mucosa / Q000187:drug effects / Q000378:metabolism / Q000473:pathology / Q000528:radiation effects; D008297:Male; D008562:Membrane Glycoproteins / Q000235:genetics / Q000378:metabolism; D026901:Membrane Transport Proteins; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D012701:Serotonin / Q000097:blood / Q000378:metabolism* / Q000494:pharmacology; D050486:Serotonin Plasma Membrane Transport Proteins; D013997:Time Factors; D014365:Tryptophan Hydroxylase / Q000235:genetics
D002352:Carrier Proteins; D008562:Membrane Glycoproteins; D026901:Membrane Transport Proteins; D009419:Nerve Tissue Proteins; D012333:RNA, Messenger; D050486:Serotonin Plasma Membrane Transport Proteins; C493232:Slc6a4 protein, rat; D012701:Serotonin; D006897:Hydroxyindoleacetic Acid; D004247:DNA; D014365:Tryptophan Hydroxylase