High Concentrations of Ketocarotenoids in Hepatic Mitochondria ofHaemorhous mexicanus

Abstract

JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org. ABSTRACTVertebrates cannot synthesize carotenoid pigments de novo, so to produce carotenoid-based coloration they must ingest carotenoids. Most songbirds that deposit red carotenoids in feathers, bills, eyes, or skin ingest only yellow or orange dietary pigments, which they oxidize to red pigments via a ketolation reaction. It has been hypothesized that carotenoid ketolation occurs in the liver of vertebrates, but this hypothesis remains to be confirmed. To better understand the role of hepatocytes in the production of ketolated carotenoids in songbirds, we measured the carotenoid content of subcellular components of hepatocytes from wild male house finches (Haemorhous mexicanus) that were molting red, ketocarotenoid-containing feathers (e.g., 3-hydroxy-echinenone). We homogenized freshly collected livers of house finches and isolated subcellular fractions, including mitochondria. We found the highest concentration of ketocarotenoids in the mitochondrial fraction. These observations are consistent with the hypothesis that carotenoid pigments are oxidized on or within hepatic mitochondria, esterified, and then transported to the Golgi apparatus for secretory processing.

Mitochondrial function, ornamentation, and immunocompetence

“…The diets of most animals contain predominantly yellow rather than red carotenoids (McGraw, ), so red‐colour displays require the metabolic conversion of yellow dietary carotenoids into red carotenoids via ketolation reactions (Brush, ). Recent evidence suggests that carotenoid ketolation occurs in mitochondria in association with complexes of the electron transport chain (Johnson & Hill, ; Ge et al, ; Lopes et al, ). The ability of animals to generate red versus yellow colouration may therefore be directly dependent on the oxidative state and membrane potential of mitochondria, such that mitochondrial dysfunction disrupts ketolation and causes a loss of red ornamentation.…”

The role of the antioxidant system during intense endurance exercise: lessons from migrating birds

“…Generally, it is thought that dietary hydrophilic antioxidants act in the bloodstream or cytoplasm, and lipophilic antioxidants are stored in cell membranes and fats, and can counteract RS within cells (Catoni et al, 2008b;Ge et al, 2015;Halliwell and Gutteridge, 2007). This, however, varies among tissues, and understanding the direct link between consumption, deposition and use is complicated by the interactive nature of these antioxidants (Bohn, 2014;Catoni et al, 2008b).…”

Plumage redness signals mitochondrial function in the House Finch

“…35 Carotenoids are responsible for the bright red, orange, and yellow coloration of many 36 animal species, and this coloration serves as an important social signal of individual condition 37 [1,2]. In many vertebrate species, individuals that display red-shifted coloration gain a mating 38 advantage or hold more resources [3,4], and carotenoid coloration is among the most commonly 39 cited example of a condition-dependent sexual ornament [5][6][7]. Compared to animals with less 40 red ornamentation, individuals with redder ornaments are better at resisting and recovering from 41 parasites and managing oxidative stress, among other measures of performance [8][9][10][11].…”

“…Citrate synthase activities was measured in liver A key prediction of the hypothesis that carotenoid coloration is linked to cellular 289 respiration is that red carotenoid pigments should be present within mitochondria [19,25]. We 290 previously documented that high levels of red ketolated carotenoids are associated with 291 mitochondria in the livers of molting house finches [39], but we could not rule out that these 292 pigments were actually concentrated in external mitochondrial-associated membranes. To 293 resolve this, we isolated and fractionated hepatic mitochondria into IMM, OMM, and matrix, and 294 subsequently measured the concentrations of the red carotenoid 3HE in the fractions.…”