Mechanism and rate of glucose absorption differ between an Australian honeyeater (Meliphagidae) and a lorikeet (Loridae)

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dc.contributor.authorNapier, K.
dc.contributor.authorMcWhorter, T.
dc.contributor.authorFleming, P.
dc.date.issued2008
dc.description.abstractEfficient mechanisms of glucose absorption are necessary for volant animals as a means of reducing mass during flight: they speed up gut transit time and require smaller volume and mass of gut tissue. One mechanism that may be important is absorption via paracellular (non-mediated) pathways. This may be particularly true for nectarivorous species which encounter large quantities of sugar in their natural diet. We investigated the extent of mediated and non-mediated glucose absorption in red wattlebirds Anthochaera carunculata (Meliphagidae) and rainbow lorikeets Trichoglossus haematodus (Loriidae) to test the hypothesis that paracellular uptake accounts for a significant proportion of total glucose uptake in these species. We found that routes of glucose absorption are highly dynamic in both species. In lorikeets, absorption of L-glucose (non-mediated uptake) is slower than that of D-glucose (mediated and non-mediated uptake), with as little as 10% of total glucose absorbed by the paracellular pathway initially (contrasting previous indirect estimates of 0%). Over time, however, more glucose may be absorbed via the paracellular route. Glucose absorption by both mediated and non-mediated mechanisms in wattlebirds occurred at a faster rate than in lorikeets, and wattlebirds also rely substantially on paracellular uptake. In wattlebirds, we recorded higher bioavailability of L-glucose (96±3%) compared with D-glucose (57±2%), suggesting problems with the in vivo use of radiolabeled D-glucose. Further trials with 3-O-methyl-D-glucose revealed high bioavailability in wattlebirds (90±5%). This non-metabolisable glucose analogue remains the probe of choice for measuring uptake rates in vivo, especially in birds in which absorption and metabolism occur extremely rapidly.
dc.description.statementofresponsibilityKathryn R. Napier, Todd J. McWhorter and Patricia A. Fleming
dc.identifier.citationThe Journal of Experimental Biology, 2008; 211(22):3544-3553
dc.identifier.doi10.1242/jeb.020644
dc.identifier.issn0022-0949
dc.identifier.issn1477-9145
dc.identifier.orcidMcWhorter, T. [0000-0002-4746-4975]
dc.identifier.urihttp://hdl.handle.net/2440/55335
dc.language.isoen
dc.publisherCompany of Biologists Ltd
dc.relation.grantARC
dc.source.urihttps://doi.org/10.1242/jeb.020644
dc.subjectparacellular absorption
dc.subjectglucose absorption
dc.subjectred wattlebird
dc.subjectAnthochaera carunculata
dc.subjectrainbow lorikeet
dc.subjectTrichoglossus haematodus
dc.subject3-O-methyl-D-glucose
dc.subjectL-glucose
dc.titleMechanism and rate of glucose absorption differ between an Australian honeyeater (Meliphagidae) and a lorikeet (Loridae)
dc.typeJournal article
pubs.publication-statusPublished

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