N. Tolosa de Talamoni

New perspectives in melatonin uses

This review summarizes the metabolism, secretion, regulation and sites of action of melatonin. An updated description of the melatonin receptors, including their signal transduction mechanisms, distribution and characterization of receptor genes, is given. Special emphasis is focused on the clinical aspects and potential uses of melatonin in the sleep-wake rhythms, in the immune function, in cancer therapy, in neuroprotection against oxidative damage and antioxidant activities in different tissues. Finally, combined effects of melatonin with other drugs are discussed.

Glutathione plays a role in the chick intestinal calcium absorption

DL-buthionine-S,R-sulfoximine (BSO) administration to vitamin D-deficient chicks treated with cholecalciferol produces a rapid decrease in the Ca2+ transfer from lumen-to-plasma and in the intestinal glutathione content. This response was reversed by addition of glutathione monoester to the intestinal sac. Variables related to the Ca2+ homeostasis such as plasma Ca and P, and intestinal calbindin D28k were not modified by BSO given to vitamin D-deficient chicks treated with cholecalciferol. Intestinal alkaline phosphatase activity, on the contrary, was highly reduced by BSO in vitamin D-deficient chicks treated with vitamin D3. This effect showed time and dose-dependency. Although the mechanism/s of action of BSO on the intestinal Ca absorption is unknown, it is quite possible that thiol groups of protein involved in the Ca2+ transport are affected by the GSH depletion and/or by block of the antioxidant ability of vitamin D3. Thus, reactive oxygen compounds would be increased and, therefore, the Ca2+ movement from lumen to plasma decreases.

Naringin prevents the inhibition of intestinal Ca 2+ absorption induced by a fructose rich diet

This study tries to elucidate the mechanisms by which fructose rich diets (FRD) inhibit the rat intestinal Ca2+ absorption, and determine if any or all underlying alterations are prevented by naringin (NAR). Male rats were divided into: 1) controls, 2) treated with FRD, 3) treated with FRD and NAR. The intestinal Ca2+ absorption and proteins of the transcellular and paracellular Ca2+ pathways were measured. Oxidative/nitrosative stress and inflammation parameters were evaluated. FRD rats showed inhibition of the intestinal Ca2+ absorption and decrease in the protein expression of molecules of both Ca2+ pathways, which were blocked by NAR. FRD rats showed an increase in the superoxide anion, a decrease in the glutathione and in the enzymatic activities of the antioxidant system, as well as an increase in the NO content and in the nitrotyrosine content of proteins. They also exhibited an increase in both IL-6 and nuclear NF-κB. All these changes were prevented by NAR. In conclusion, FRD inhibit both pathways of the intestinal Ca2+ absorption due to the oxidative/nitrosative stress and inflammation. Since NAR prevents the oxidative/nitrosative stress and inflammation, it might be a drug to avoid alteration in the intestinal Ca2+ absorption caused by FRD.

Melatonin: A protective hormone of intestinal calcium absorption?

Introduction: Osteogenesis distraction (DO) is a surgical technique that allows distraction of the fracture callus. It has been used extensively in endochondral long bones but not in the craniofacial skeleton of endomembranous origin. Mandibular alveolar bone of endomembranous origin contains teeth sockets; it is a functional bone that undergoes bone turnover at a higher rate than other bone tissues. The aim of our work was to present the development of an experimental model of DO in rat mandibular alveolar bone including all stages, i.e. animal procedures, laboratory determinations, histological procedures and histomorphometric measurements. Methods: 8 Wistar rats, 80 g bw, underwent extraction of all mandibular molars. At 400 g bw, right hemimandibular osteotomy was performed and the device was placed. After 6 days (latency) it was activated (0.175 mm/d once a day/ 6 days) and then left in place 28 days (consolidation phase). Rats were sacrificed and hemimandibles were resected. The technique was standardized to perform radiographs and hemimandible orientation was adjusted to allow obtaining comparable histologic sections. A method to record and compare these measurements was designed. H&E stained mesiodistally oriented hemimandible sections were obtained. Screw loosening and loss of the device during the consolidation phase were initial problems (SAIO, 2008). The original design was perfected to avoid mobility. Results: The new, improved device remained in place throughout the experiment. Comparable mesiodistally oriented sections were obtained. Conclusion: This experimental model of mandibular DO will allow studying the cellular and molecular events that take place during DO under different experimental conditions. This article is part of a Special Issue entitled AAOMM 2010 Abstracts.

Sodium deoxycholate alters the transcellular pathway of intestinal calcium absorption

Diabetes mellitus (DM) type I is a disorder characterized by hyperglycemia due to a deficient insulin secretion. Alterations in different organs have been observed in DM. The aim of this work was to study intestinal calcium absorption, alkaline phosphatase (AP) activity and the expression of some genes involved in calcium transport in an experimental diabetes model. Two-month old male Wistar rats were divided into two groups: control (n=5) and treated rats (n=5). Diabetes was induced by intraperitoneal injection of streptozotocin (STZ) (60 mg/kg) after fasting for 12-hours. Control rats were injected with the vehicle. Serum and urine glucose were determined before and 5 days after STZ induction. Rats with glycemia over 250 mg/dL were considered diabetic. Intestinal calcium absorption was measured and AP activity from duodenal mucosa was assayed. Ca-ATPase pump and calbindin D28K gene expressions were analyzed by RT-PCR. The weight of the STZ-injected rats decreased after 5 days of the induction and the glucose levels were significantly higher than those of the control group (406±13 mg/dL vs 142±17 mg/dL, p<0.001). Diabetic rats had polyuria and glycosuria. Calcium absorption was lower in diabetic rats than in controls (0.26±0.01 nmol Ca/mL plasma vs 0.65±0.05 nmol Ca/mL plasma, p<0.001). AP activity was significantly lower in diabetic rats than in controls (0.31±0.06 IU/mg protein vs 0.59±0.10 IU/mg protein, p<0.05). Preliminary determinations show that the expression of the studied genes would be similar in both groups. To conclude, the metabolic alteration in DM would alter intestinal calcium absorption and AP activity. The molecular mechanisms responsible of these effects are under investigation. This article is part of a Special Issue entitled AAOMM 2010 Abstracts.