RESUMO
In order to reveal the participation of extrapineal melatonin in ageing processes, Wistar rats were (a) exposed to small doses of gamma irradiation and (b) subjected to pinealectomy. It was showed that during a radiation-induced aging simulation occurs a manifest hypoplasia of MT-responder cells in the mucosa of the duodenum, and the number of mast cells is reduced by ten times. During pinealectomy the number of MT-positive enterochromaffin cells increases.
Assuntos
Senilidade Prematura/metabolismo , Envelhecimento/metabolismo , Raios gama , Melatonina/biossíntese , Glândula Pineal , Envelhecimento/efeitos da radiação , Senilidade Prematura/etiologia , Animais , Modelos Animais de Doenças , Duodeno/metabolismo , Duodeno/efeitos da radiação , Células Enterocromafins/metabolismo , Células Enterocromafins/efeitos da radiação , Masculino , Mastócitos/metabolismo , Mastócitos/efeitos da radiação , Glândula Pineal/metabolismo , Glândula Pineal/cirurgia , Ratos , Ratos WistarRESUMO
PURPOSE: 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. MATERIALS AND 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.
Assuntos
Colo/metabolismo , Colo/efeitos da radiação , Proteínas de Membrana Transportadoras , Serotonina/metabolismo , Animais , Sequência de Bases , Proteínas de Transporte/genética , Proteínas de Transporte/metabolismo , Divisão Celular/efeitos da radiação , Colo/efeitos dos fármacos , Colo/patologia , DNA/genética , Células Enterocromafins/metabolismo , Células Enterocromafins/patologia , Células Enterocromafins/efeitos da radiação , Potenciais Evocados/efeitos dos fármacos , Potenciais Evocados/efeitos da radiação , Expressão Gênica/efeitos da radiação , Ácido Hidroxi-Indolacético/sangue , Ácido Hidroxi-Indolacético/metabolismo , Mucosa Intestinal/efeitos dos fármacos , Mucosa Intestinal/metabolismo , Mucosa Intestinal/patologia , Mucosa Intestinal/efeitos da radiação , Masculino , Glicoproteínas de Membrana/genética , Glicoproteínas de Membrana/metabolismo , Proteínas do Tecido Nervoso/genética , Proteínas do Tecido Nervoso/metabolismo , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , Ratos , Ratos Wistar , Serotonina/sangue , Serotonina/farmacologia , Proteínas da Membrana Plasmática de Transporte de Serotonina , Fatores de Tempo , Triptofano Hidroxilase/genéticaRESUMO
The effects of a single 400 R whole-body dose of X-irradiation on the regional 5HT content of the gastrointestinal (G. I.) tract were studied from four hours to 40 days after irradiation. The total 5HT content of various G.I. tissues was determined and 5HT was also determined per unit of body weight, wet weight of tissue and tissue protein. Irradiation caused an immediate decrease of the amine content of various G.I. regions in adult rats. This was followed by recovery, the degree of which varied in different regions. Some minor morphological changes were seen in enterochromaffin cells one and two days after irradiation but not later. The effects of irradiation on the G.I. tissues were stronger in young rats, in whom no complete recovery of 5HT occurred within 45 days. The present results support the view that irradiation exerts a direct damaging effect on the gastrointestinal 5HT storage, which is associated with liberation of 5HT from amine-containing cells. The duration of the effect varies with age and intestinal segment concerned.