Heterogeneous expression of melatonin receptor MT1 mRNA in the rat intestine under control and fasting conditions

Abstract

Melatonin is found in mammalian central nervous system and various peripheral tissues including gastrointestinal tract (GIT) where it participates in the regulation of intestinal motility, blood flow, immunomodulation, ion transport, cell proliferation and scavenging of free radicals. Some of these effects are achieved via melatonin binding to specific receptors, MT1 and MT2. As no thorough study on the expression of these receptors in the GIT has yet been done, the aim of this study was to determine the MT1 mRNA expression in the rat intestine under both control and fasting conditions. Our results suggest that MT1 mRNA is present in epithelial as well as subepithelial layer, with higher expression in the latter in all intestinal segments studied. The highest signal of the MT1 transcript along the rostro-caudal intestinal axis was found both in epithelial and subepithelial layers of the duodenum. Nevertheless, duodenal MT1 mRNA expression did not reach the level found in pituitary gland. In a 12:12-hr light:dark cycle a MT1 receptor expression in the subepithelial layer of rat distal colon did not manifest a significant diurnal rhythm. Short-term fasting increased the expression of MT1 transcript in the subepithelial layer of both the small and large intestine. During long-term fasting the increase persisted only in distal colon while a return to control levels was observed in small intestinal segments. In conclusion we demonstrated heterogeneous expression of MT1 receptor in the rat intestine and showed that its expression is up-regulated by nutritional deprivation.

Protective effect of melatonin in acetic acid induced colitis in rats

“…Distribution of melatonin receptors in the colon compartments is not known, although it could indicate the function of melatonin in this organ. The only study [53] dealing with this problem indicates a high density of melatonin-binding sites in colonic blood vessels. Therefore, the modulation of vascular supply may represent one way of melatonin action in the colon.…”

Effects of nutrient restriction and melatonin supplementation on maternal and foetal hepatic and small intestinal energy utilization

“…Asymmetrical growth of foetuses' organs during development may impact the difference in results obtained in different studies. The increase in maternal and foetal organ mass with melatonin supplementation when dams were fed adequate nutrients may be related to the ability of melatonin in the GIT (Bubenik et al., ; Huether, ) to increase absorption of nutrients (Sotak et al., ; Song et al., ). In livestock species, timing and rate of foetal GIT maturation is dependent on enteral nutrient intake, which takes place both pre‐ and post‐natally (Sangild et al., ).…”

Effects of Fasting at Different Stages of Lighting Regimen on the Proliferation of Jejunal Epithelial Cells During Rat Pup Weaning

“…On the other hand, melatonin is most highly expressed in the gastrointestinal tract (Hoogerwerf,2007), and there appears to be a circadian rhythm to expression levels in birds and rodents, with high expression levels occurring in the dark period (Lee and Pang,1993). Soták et al (2006) demonstrated that melatonin expression is controlled by feeding, based on their observation that short‐ or long‐term fasting increased the expression of the melatonin receptor in rat intestines.…”

“…The relationship between these factors might also be important as early as the weaning phase and could control the circadian rhythms of specific process such as cell proliferation. Given that melatonin is regulated by food (Stokkan et al,2001; Kobayashi et al,2004; Soták et al,2006) and that melatonin decreases cell proliferation, it is possible that the already high levels of melatonin expression seen during the dark period (Lee and Pang,1993) increase even more in the absence of food. This additional increase in melatonin levels, therefore, could increase the rate of cell proliferation in the fasting group at 02:00 hr, but this suggestion must be further explored.…”

“…Therefore, it is not surprising that there is a coupling between the suprachiasmatic control of circadian variation and the peripheral circadian controllers located in the organs of the digestive system, such as the small intestine and liver. In the digestive tract, food is the stronger pacemaker, and it has been demonstrated that feeding restrictions can shift clock gene rhythmicity and melatonin expression (Stokkan et al,2001; Kobayashi et al,2004; Soták et al,2006; Hoogerwerf,2006).…”