Metabolism of Melatonin Synthesis-Related Indoles in the Turkey Pineal Organ and Its Modification by Monochromatic Light.

The metabolism of pineal indoles is closely related to alterations in the light and dark phases of a daily cycle. Recent research showed important interspecies differences in the pineal biochemistry, and a strong impact of monochromatic light on many physiological processes in birds. Therefore, the aims of study were to characterize the metabolism of melatonin-synthesis indoles in the pineal organ of the domestic turkey, and to determine the changes occurring in this metabolism under the influence of different wavelengths and intensities of light. For this purpose, 3-week-old turkeys were kept under 16 lx white light, or under blue, green, and red light with intensities of 16, 32, and 64 lx during the photophase, and after 7 d were sacrificed at 4 h intervals. The activities of melatonin-synthesizing enzymes and the contents of indoles were measured in the same pineal organ. The results revealed that the activities of tryptophan hydroxylase and arylalkylamine N-acetyltransferase, and the levels of all tryptophan derivatives had significant daily changes in birds kept under each light condition used. The profile of pineal indole metabolism in 4-week-old turkeys was characterized by high-amplitude rhythms in the activity of arylalkylamine N-acetyltransferase and the contents of N-acetylserotonin and melatonin, equal relative amounts of serotonin and 5-hydroxyindoleacetic acid, and higher content of melatonin than N-acetylserotonin. The monochromatic light significantly modified the pineal indole metabolism, and its effects were dependent on the color and intensity of light. Pronounced changes occurred in the level of serotonin synthesis and the daily rhythm course of melatonin synthesis.

Embryonic Ontogeny of 5-Hydroxyindoles and 5-Methoxyindoles Synthesis Pathways in the Goose Pineal Organ.

The aim of this study was to characterize the embryonic ontogeny of 5-hydroxyindoles and 5-methoxyindoles synthesis pathways in the goose pineal organ. The study was performed on embryos aged 14-28 days, which have been incubated under a 12L:12D cycle. The pineal organs were collected for measurements of indole content by HPLC every 6 h on embryonic day (ED) 14, ED 16, ED 18 and ED 22 or every 2 h on ED 24, ED 26 and ED 28. The level of tryptophan showed no significant changes during development and no day-night variations. The content of 5-hydroxytryptophan increased between ED 14 and ED 26. It was significantly higher during scotophase than during photophase starting from ED 14. The serotonin content was low during the early stages of development (ED 14-ED 18) and prominently increased from ED 20. The serotonin levels also showed day-night differences; however, they were less conspicuous than those of 5-hydroxytryptophan. The changes in the level of 5-hydroxyindole acetic acid were similar to those of serotonin. 5-Hydroxytryptophol was measurable from ED 18. Levels of N-acetylserotonin, which were detectable for the first time on ED 16, prominently increased between ED 22 and ED 28 and showed significant day-night differences from ED 20. Melatonin was detectable from ED 18. Like N-acetylserotonin, its content increased rapidly between ED 22 and ED 28, and from ED 20 showed diurnal variations. 5-Methoxyindole acetic acid and 5-methoxytryptophol occurred at measurable levels from ED 18 and ED 26, respectively. The obtained results showed that embryonic development of indole metabolism in the goose pineal organ starts with the beginning of serotonin synthesis. The processes of serotonin acetylation and 5-hydroxyindoles methylation were turned on later. Diurnal rhythmicity develops very early in the embryonic pineal organ of the goose when the eggs are incubated under a 12 h light: 12 h dark schedule. Two processes are responsible for generation of the diurnal rhythms of 5-hydroxyindoles and 5-methoxyindoles: (i) hydroxylation of tryptophan and (ii) acetylation of serotonin.

Effects of Streptozotocin-Induced Diabetes on the Pineal Gland in the Domestic Pig.

Several observations from experiments in rodents and human patients suggest that diabetes affects pineal gland function, including melatonin secretion; however, the accumulated data are not consistent. The aim of the present study was to determine the effects of streptozotocin-induced diabetes on the pineal gland in the domestic pig, a species widely used as a model in various biomedical studies. The study was performed on 10 juvenile pigs, which were divided into two groups: control and diabetic. Diabetes was evoked by administration of streptozotocin (150 mg/kg of body weight). After six weeks, the animals were euthanized between 12.00 and 14.00, and the pineal glands were removed and divided into two equal parts, which were used for biochemical analyses and for preparation of explants for the superfusion culture. The pineal contents (per 100 µg protein) of serotonin, 5-hydroxyindole acetic acid, 5-hydroxytryptophol, 5-methoxyindole acetic acid, 5-methoxytryptophol, and 5-methoxytryptamine were significantly lower in diabetic pigs than in control pigs. In contrast, the level of N-acetylserotonin was significantly higher in diabetic animals. No significant differences were found in the level of melatonin between control and experimental pigs. The amounts of 3,4-dihydroxyphenylalanine, dopamine, norepinephrine, and 3,4-dihydroxyphenylacetic acid were significantly lower in the pineal glands of diabetic animals. The level of vanillylmandelic acid was higher in diabetic pigs. No differences were observed in the level of basal and NE-stimulated release of N-acetylserotonin or melatonin between the pineal explants prepared from control and experimental animals. In vitro treatment with insulin was ineffective. In conclusion, streptozotocin-induced diabetes affects both indole metabolism and adrenergic neurotransmission in the pig pineal gland.

The Effects of Deoxynivalenol and Zearalenone on the Pig Large Intestine. A Light and Electron Microscopy Study.

The contamination of feed with mycotoxins results in reduced growth, feed refusal, immunosuppression, and health problems. Deoxynivalenol (DON) and zearalenone (ZEN) are among the most important mycotoxins. The aim of the study was to examine the effects of low doses of these mycotoxins on the histological structure and ultrastructure of the large intestine in the pig. The study was performed on 36 immature gilts of mixed breed (White Polish Big × Polish White Earhanging), which were divided into four groups administrated per os with ZEN at 40 µg/kg BW, DON at 12 µg/kg BW, a mixture of ZEN (40 µg/kg BW) and DON (12 µg/kg BW) or a placebo. The pigs were killed by intravenous overdose of pentobarbital after one, three, and six weeks of treatment. The cecum, ascending and descending colon samples were prepared for light and electron microscopy. Administration of toxins did not influence the architecture of the mucosa and submucosa in the large intestine. ZEN and ZEN + DON significantly decreased the number of goblet cells in the cecum and descending colon. The mycotoxins changed the number of lymphocytes and plasma cells in the large intestine, which usually increased in number. However, this effect differed between the intestine segments and toxins. Mycotoxins induced some changes in the ultrastructure of the mucosal epithelium. They did not affect the expression of proliferative cell nuclear antigen and the intestinal barrier permeability. The obtained results indicate that mycotoxins especially ZEN may influence the defense mechanisms of the large intestine.