title: Seasonal changes in the activity of the adrenal medulla of Viscacha (Lagostomus maximus maximus).
abstract: Animals living in nontropical climates modify their physiology and behavior to adapt to seasonal environmental changes. Part of this adaptation involves the release of catecholamine from sympathetic nerve endings and the adrenal medulla, which play a major role in regulating energy balance. The aim of this work was to investigate whether adult male viscachas in their natural habitat exhibits structural changes in the adrenal medulla during the annual seasonal cycle. In August-September, chromaffin granules revealed ultrastructural changes suggestive of piecemeal degranulation. Quantitative morphometric analysis by transmission electron microscopy showed a significantly lower percentage of resting chromaffin granules and a higher percentage of altered granules and empty containers in August-September (late winter) compared to February-March (late summer), suggesting an increased secretory process of catecholamines in August-September. The mechanism of piecemeal degranulation might amplify this process, encouraging the adaptive response to winter environmental conditions. Tissue levels of epinephrine, norepinephrine, and dopamine (analyzed by high-performance liquid chromatography) changed throughout the year, reaching maximum values in February-March and minimum values in August-September. These results demonstrate morphological and biochemical seasonal variations of the adrenal medulla, suggesting that epinephrine might promote energy mobilization, which allow the Lagostomus to cope with adverse environmental conditions and thus to survive during winter season.
authors: Facultad de Química, Bioquímica y Farmacia, Laboratorio de Histología, Universidad Nacional de San Luis, Av. Ejército de los Andes 950, Bloque I, 1º piso, 5700 San Luis, Argentina.
authors: Hugo
authors: H
authors: Rodriguez
authors: Verónica Palmira
authors: VP
authors: Filippa
authors: Alicia
authors: A
authors: Penissi
authors: Teresa
authors: T
authors: Fogal
authors: Susana
authors: S
authors: Domínguez
authors: Ramón Salvador
authors: RS
authors: Piezzi
authors: Luis
authors: L
authors: Scardapane
mesh_terms: D000222:Adaptation, Physiological; D000313:Adrenal Medulla / Q000378:metabolism* / Q000648:ultrastructure; D000818:Animals; D002395:Catecholamines / Q000378:metabolism*; D015550:Cell Degranulation; D002837:Chromaffin Granules / Q000378:metabolism* / Q000648:ultrastructure; D002851:Chromatography, High Pressure Liquid; D004298:Dopamine / Q000378:metabolism; D004734:Energy Metabolism; D004837:Epinephrine / Q000378:metabolism; D008297:Male; D046529:Microscopy, Electron, Transmission; D009638:Norepinephrine / Q000378:metabolism; D011891:Rain; D012377:Rodentia / Q000378:metabolism*; D012621:Seasons; D013472:Sunlight; D013696:Temperature; D013997:Time Factors
chemical_list: D002395:Catecholamines; D004298:Dopamine; D009638:Norepinephrine; D004837:Epinephrine