Table 1.
Oligonucleotide sequences used for Reverse transcriptase PCR.
Figure 1.
Glucose transporter mRNA expression in hummingbird tissues.
Agarose gels (1.5%) of RT-PCR products for a) GLUT1 (340 bp), b) GLUT2 (305 bp), c) GLUT3 (543 bp), and d) GLUT4 (449 bp, expected product size from mouse), and e) GAPDH (585 bp). A 100 bp ladder was run in lane 1 of each gel. PCR reactions were performed on cDNA from hummingbird pectoralis (P), brain (B), heart (H), liver (L), ankle-extensor group muscles (G; e.g. gastrocnemius and soleus), wrist-extensor group muscle (E; e.g. extensor digitorum longus), kidney (K), and intestine (I), as well as cDNA from mouse cardiac tissue (MH; GLUT4 gel only) and samples of the reaction mixture were run in other lanes. Identical patterns of expression were observed using samples isolated from tissues of zebra finches (data not shown). Due to insufficient numbers of lanes per gel or because small tissue masses necessitated pooling of samples from 2 individuals, reaction products from some samples had to be run on separate gels. These are indicated by breaks in the image and by asterisks next to the lane headings (e.g. E*).
Table 2.
GLUT cDNA sequence identities.
Figure 2.
Glucose transporter protein expression in hummingbird tissues.
Western blots using primary antibodies against a) GLUT1, b) GLUT4, and c) GAPDH. Samples were included from hummingbird pectoralis (P), brain (B), heart (H), liver (L), and for GLUT4 only, intestine (I) and kidney (K). Blots for GLU1 (a) and GAPDH (c) include samples from two different individual hummingbirds (e.g. P1 and P2). Samples from mouse (M) soleus (a, c) and cardiac (b) tissue are included as positive controls.
Table 3.
GLUT amino acid sequence identities and similarities.
Figure 3.
Glucose transporter staining in hummingbird and mouse skeletal muscle.
Immunohistochemically-stained cross-sections of hummingbird pectoralis (a, c) and mouse gastrocnemius (b, d) muscle. Panels a and b) Immunostaining of tissues with GLUT1 primary antibody, visualized with a FITC-conjugated secondary antibody (green). Panels c and d) Immunostaining of tissues with GLUT4 primary antibody, visualized with a FITC-conjugated secondary antibody (green). Note, GLUT1 staining of the hummingbird pectoralis (a) is homogenous, and fiber sizes are all similar, reflecting the homogeneity of fiber type (type IIa; Fast oxidative-glycolytic). GLUT1 (and GLUT4) staining in the mouse gastrocnemius (b, d) is heteogenous and fiber diameters are varied, reflecting the diverse fiber type makeup of this muscle. Hummingbird pectoralis exhibited no staining using the GLUT4 antibody (intensity similar to use of secondary antibody alone; data not shown). Tissues in each panel were counterstained with DAPI in order to visualize nuclei (blue).
Figure 4.
Visualization of capillaries in hummingbird and mouse skeletal muscle.
Cross-sections of hummingbird pectoralis (a) and mouse gastrocnemius (b) muscle subjected to Periodic Acid-Schiff staining to visualized capillaries. Staining was much more intense in the hummingbird tissue reflecting the relatively greater capillary density in this tissue.
Figure 5.
Glucose transporter staining in hummingbird and mouse liver.
Sections of hummingbird (a) and mouse (b) liver tissue stained with GLUT1 primary antibody. Staining was visualized with a FITC-conjugated secondary antibody (green). Sections were counterstained with DAPI to visualize nuclei (blue).
Figure 6.
Glucose transporter staining in hummingbird heart and brain.
Sections of hummingbird (a) heart and (b) brain tissue stained with GLUT1 primary antibody. Staining was visualized with a FITC-conjugated secondary antibody (green). Sections were counterstained with DAPI to visualize nuclei (blue).