Nitric oxide regulates mitochondrial re-modelling in interscapular brown adipose tissue: ultrastructural and morphometric-stereologic studies

• Published in: Journal of microscopy (Oxford) 2008-12, Vol.232 (3), p.542-548
• Main Authors: Petrovic, V, Korac, A, Buzadzic, B, Vasilijevic, A, Jankovic, A, Micunovic, K, Korac, B
• Format: Article
• Language: English
• Subjects: Adipose Tissue - metabolism; Adipose Tissue - ultrastructure; Animals; Arginine - metabolism; Biometry; Brown adipocytes; electron microscopy; Male; Microscopy, Electron, Transmission; Mitochondria - metabolism; Mitochondria - ultrastructure; mitochondriogenesis; NG-Nitroarginine Methyl Ester - metabolism; nitric oxide; Nitric Oxide - metabolism; Rats
• ISSN: 0022-2720; 1365-2818
• DOI: 10.1111/j.1365-2818.2008.02132.x

As a complex, cell-specific process that includes both division and clear functional differentiation of mitochondria, mitochondriogenesis is regulated by numerous endocrine and autocrine factors. In the present ultrastructural study, in vivo effects of l-arginine-nitric oxide (NO)-producing pathway on mitochondriogenesis in interscapular brown adipose tissue (IBAT) were examined. For that purpose, adult Mill Hill hybrid hooded rats were receiving l-arginine, a substrate of NO synthases (NOSs), or Nω-nitro- l-arginine methyl ester ( l-NAME), an inhibitor of NOSs, as drinking liquids for 45 days. All experimental groups were divided into two sub-groups - acclimated to room temperature and cold. IBAT mitochondria were analyzed by transmission electron microscopy and stereology. l-Arginine treatment acted increasing the number of mitochondrial profiles per cell profile, as well as volume fraction of mitochondria per cell volume in animals maintained at room temperature. Cold-induced enhancement of number of mitochondrial profiles per cell profile was additionally increased in l-arginine-treated rats. Ultrastructural examinations of l-arginine-treated cold-acclimated animals clearly demonstrated thermogenically active mitochondria (larger size, lamellar, more numerous and well-ordered cristae in their profiles), which however were inactive in l-arginine-receiving animals kept at room temperature (small mitochondria, tubular cristae). By contrast, l-NAME treatment of rats acclimated to room temperature induced mitochondrial alterations characterized by irregular shape, short disorganized cristae and megamitochondria formation. These results showed that NO is a necessary factor for mitochondrial biogenesis and that it acts intensifying this process, but NO alone is not a sufficient stimulus for in vivo induction of mitochondriogenesis in brown adipocytes.