Effects of L-glutamine supplementation on the myenteric neurons from the duodenum and cecum of diabetic rats / Efeitos da suplementação com L-glutamina sobre os neurônios mioentéricos do duodeno e jejuno de ratos diabéticos

CONTEXT: Peripheral neuropathy is one of the chronic complications of diabetes mellitus and is directly related to gastrointestinal consequences of the disease. Myenteric neurons are affected in some pathological conditions such as diabetic neuropathy. The imbalance between cellular antioxidants and free radicals, leading to an increase in oxidative stress, is considered one of the main factors responsible for neuronal damages in diabetes. Drugs that reduce the oxidative stress may play a significant role in the treatment of neurological complications of diabetes mellitus. OBJECTIVE: To evaluate the effect of L-glutamine supplementation on the myenteric neurons from the cecum and duodenum of Wistar rats with streptozotocin-induced diabetes mellitus. METHODS: The animals were divided in four groups (n = 5): non-treated normoglycemics, normoglycemics treated with L-glutamine, non-treated diabetics and diabetics treated with L-glutamine from the 4th day of diabetes induction on. The amino acid L-glutamine was added to their diet at 1 percent. Giemsa's technique was employed to stain the myenteric neurons. We determined the cell body area of 500 neurons in each group studied. The quantitative analysis was performed by sampling in an area of 16.6 mm² in the cecum and 3.6 mm² in the duodenum of each animal. RESULTS: After the supplementation with L-glutamine in the duodenum, we observed a preservation of neuronal density in groups normoglycemic and diabetic (P<0.05). We also observed a preservation of the cell bodies area in diabetic animals (group treated with L-glutamine) (P<0.05). In the cecum, that preservation was not evident. CONCLUSION: Supplementation with L-glutamine (1 percent) promoted a neuroprotective effect on the myenteric neurons from the duodenum of rats, both in terms of natural aging and of diabetes mellitus.

CONTEXTO: Os neurônios entéricos são afetados em condições patológicas, como a neuropatia diabética. A neuropatia periférica é uma das complicações crônicas do diabetes mellitus e está diretamente relacionada com as manifestações gastrointestinais da doença. O desequilíbrio entre antioxidantes celulares e radicais livres, com o consequente aumento do estresse oxidativo, é considerado um dos principais responsáveis pelas alterações neuronais provocadas pelo diabetes. Drogas que reduzem o estresse oxidativo podem ter papel relevante no tratamento das complicações neurológicas do diabetes mellitus. OBJETIVO: Avaliar os efeitos da suplementação com L-glutamina sobre os neurônios mioentéricos do ceco e duodeno de ratos Wistar com diabetes mellitus induzido pela estreptozootocina. MÉTODOS: Os animais foram divididos em quatro grupos (n = 5): normoglicêmicos, normoglicêmicos suplementados com L-glutamina, diabéticos, diabéticos suplementados com L-glutamina a partir do 4º dia da indução do diabetes. O aminoácido L-glutamina foi adicionado à ração na quantidade de 1 por cento. A técnica de Giemsa foi utilizada para evidenciar os neurônios mioentéricos. Foram avaliadas as áreas de corpos celulares de 500 neurônios em cada grupo estudado. A análise quantitativa foi realizada em uma área de 16,6 mm² no ceco e 3,6 mm² no duodeno de cada animal. RESULTADOS: Após suplementação com L-glutamina verificou-se no duodeno a preservação da densidade neuronal tanto nos animais normoglicêmicos quanto nos animais diabéticos (P<0,05), e também o restabelecimento da área do corpo celular nos animais diabéticos (P<0,05). No ceco esta preservação e restabelecimento não foram evidenciados. CONCLUSÃO: A suplementação com L-glutamina (1 por cento) teve efeito neuroprotetor sobre os neurônios mioentéricos do duodeno tanto em condições de envelhecimento natural como no diabetes mellitus.

Efeitos da desnervação intrínseca do jejuno após enterectomia extensa na síndrome do intestino curto em ratos / Effects of intrinsic denervation of the jejunum after extensive enterectomy in the rat bowel syndrome

OBJETIVO: Investigar em ratos Wistar as respostas adaptativas da mucosa em conseqüência da desnervação intrínseca do jejuno após ressecção intestinal extensa. MÉTODOS: Utilizaram-se 30 ratos distribuídos em três grupos segundo o procedimento realizado: C (controle), R (ressecção intestinal) e D (ressecção intestinal e desnervação intrínseca do jejuno). Posteriormente foi avaliado o ganho de peso e realizado estudos morfométrico da mucosa intestinal. RESULTADOS: Os animais do grupo D apresentaram ganho ponderal consideravelmente maior do que os do grupo R (D=312,2±21g e R=196,7±36,2g). A contagem neuronal mostrou diminuição na população de neurônios mientéricos no grupo D (344,8±34,8 neurônios/mm de jejuno) em relação aos outros grupos (R=909,0±55,5 e C=898,5±73,3). A área do epitélio da mucosa jejunal foi maior no grupo D (10,8±4,3mm²) em comparação aos grupos R (7,3±3,9mm²) e C (5,8±3,0mm²). O índice de proliferação celular epitelial da mucosa foi maior no grupo D (48,7 por cento), em relação aos grupos R (31,9 por cento) e C (23,6 por cento). CONCLUSÕES: O modelo experimental mostrou-se eficaz em melhorar o ganho ponderal dos animais submetidos à ressecção intestinal extensa, provocando intensificação da resposta hiperplásica da mucosa, a qual provavelmente levou a aumento da superfície de absorção de nutrientes. Abrem-se boas perspectivas para novas abordagens cirúrgicas para a síndrome do intestino curto.

Crotoxin, the major toxin from the rattlesnake Crotalus durissus terrificus, inhibits 3H-choline uptake in guinea pig ileum

We examined the effect of crotoxin, the neurotoxic complex from the venom of the South American rattlesnake Crotalus durissus terrificus, on the uptake of 3H-choline in minces of smooth muscle myenteric plexus from guinea pig ileum. In the concentration range used (0.03-1 ÁM) and up to 10 min of treatment, crotoxin decreased 3H-choline uptake by 50-75 percent compared to control. This inhibition was time dependent and did not seem to be associated with the disruption of the neuronal membrane, because at least for the first 20 min of tissue exposure to the toxin (up to 1 ÁM) the levels of lactate dehydrogenase (LDH) released into the supernatant were similar to those of controls. Higher concentrations of crotoxin or more extensive incubation times with this toxin resulted in elevation of LDH activity detected in the assay supernatant. The inhibitory effect of crotoxin on 3H-choline uptake seems to be associated with its phospholipase activity since the equimolar substitution of Sr2+ for Ca2+ in the incubation medium or the modification of the toxin with p-bromophenacyl bromide substantially decreased this effect. Our results show that crotoxin inhibits 3H-choline uptake with high affinity (EC25 = 10 +/- 5 nM). We suggest that this inhibition could explain, at least in part, the blocking effect of crotoxin on neurotransmission

Dietary sodium intake induced myenteric neuron hypertrophy in Wistar rats

In the present study we investigated the effect of salt intake on myenteric neuron size of the colon of adult male Wistar rats. The animals were placed on either a high-salt (HS; 8 percent; 12 animals) or a low-salt diet (LS; 0.15 percent; 12 animals) for 15 or 52 weeks and blood pressure was measured. The sizes of myenteric neurons of the distal colon from both groups were measured. No difference in neuron size was observed between the HS and LS groups after 15 weeks. After 52 weeks on HS, neuron size was increased (P<0.005) when compared with the LS group. The rats also presented hypertension, which was significantly different at 52 weeks (142 +/- 11 vs 119 +/- 7 mmHg). These results suggest that a long time on an HS diet can significantly increase myenteric nerve cell size.

Morphological and quantative study of the myenteric plexus of the duodenum of streptozotocin-induced diabetic rats

The purpose of this work was to study the morphological and quantitative alterations of the myenteric plexus neurons of the duodenum of rats with acute and chronic streptozotocin-induced diabetes and establish a comparison with non-diabetic animals. Samples of duodenum were destined to histological sections stained by Hematoxilin-Eosin and to membrane preparings stained by the Giemsa and NADH-diaphorasis methods. Semall, medium and large neurons were found, with a predominance of medium ones on chronic and acute diabetic animals. It was verified that most of the neurons of diabetic and non-diabetic animals have an eccentrical nucleus and thus this characteristic is not an indicative of degenerative process. It was observed that in diabetes there is a decrease in the number of myenteric neurons. It is argued that this initial decrease is due to the toxic effects of the drug and not to the physiopathology of diabetes itself, and also that the expressive smaller proportion of neurons on the chronically diabetic animals is due to the immediate loss related to streptozotocin and the further consequences of aging during nine weeks of diabetes.