Are there histological changes in the intestine of birds in a stress situation?

Abstract

Any alteration of homeostatic stability is a stressful situation for living beings. This alteration triggers physiological changes inresponse to a stress situation. In birds this response is related to the release of glucocorticoids. Glucocorticoids influence the functionof several tissues. Although there are a large number of studies that have investigated histological alterations of glucocorticoids inmammals, the knowledge of this area in birds is limited. The main glucocorticoid in birds is corticosterone (CORT). In previousexperiments our research group found a marked relationship between treatment with CORT and an increase in the heterophil tolymphocyte index (H/L), an indicator of stress in birds. We found a decrease in body mass when the birds were treated with CORT;however, the intestine mass was not affected by CORT treatments. The objective of this work was to determine histological alterationin the intestine of Passer domesticus in response to different doses of exogenous CORT. To achieve our goal, 16 sparrows wereacclimated to a laboratory condition with water and food ad libitum, them separating randomly in four groups and each group wereexposed to a different concentration of CORT in drinking water ad libitum (control, 20, 40 and 80 mg/l) for 72 hours emulating a longterm stress situation. After the exposition the intestine was removed and a portion of proximal section was fixed in Bouin solution.Then the intestinal pieces were dehydrated and embedded in paraffin. Histological studies were performed on 5µm sections, stainedby hematoxylin-eosin coloration, and examined by a light microscope. A morphometric analysis was performed using the softwareImage Pro Plus 5.0. The measured parameters were: intestinal perimeter, muscle layer, mucosa thickness, crypt width, villus width andvillus height. The data were statistically analyzed by ANOVA with Tukey post-hoc test (p<0.05). Our results showed a proportionalincrease in the H/L index in concordance with CORT treatments. The crypt width significantly decreased in birds exposed to 80 mg/lof CORT. However, the other parameters did not show significant variation. In conclusion the effect of CORT in the H/L index checksthe effectiveness of the treatment. The decrease in the width of the crypts could be related to an effect at the level of enterocyte renewal.This fact may indicate the first event of a histological alteration in the intestine of Passer domesticus. Supported by CyT-UNSLPROICO 2-0516 and FONCYT PICT-201?0595.