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Characterization of sodium‐glucose co‐transporters in the avian kidney
Author(s) -
Sweazea Karen L.,
Casotti Giovanni,
Braun Eldon J.
Publication year - 2006
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.20.5.a1466
Subject(s) - nephron , fowl , kidney , population , medicine , glucose transporter , biology , endocrinology , sodium , antibody , renal function , chemistry , immunology , insulin , ecology , environmental health , organic chemistry
Allometric analyses have shown that the glomerular filtration rates of birds and mammals are similar; however, these two groups differ markedly with respect to plasma glucose concentrations, birds having much higher concentrations. Despite the fact that the filtered loads of glucose are much greater for birds, little or no glucose appears in their ureteral urine suggesting that the avian kidney has a large capacity to reabsorb glucose. Data from previous work indicates that the tubular maximum for glucose transport by the white leghorn domestic fowl kidney is about 26 mg/min, a value about five times higher that the same parameter for the human kidney, supporting this assertion. In mammals, glucose is reabsorbed in the proximal renal tubule by sodium‐glucose co‐transport proteins (SGLT‐1 and SGLT‐2) that have been extensively characterized. Although some form of SGLTs must be present in the avian kidney, they have yet to be described. As a first approach to determining the presence and nature of avian glucose transport proteins, we have begun immunocytochemical studies to localize them in the heterogeneous nephron population within avian kidneys. As the identity of the proteins is unknown in birds and there are no available antibodies, we used antibodies to rabbit SGLT‐1 and ‐2 for our study. The results indicate a weak presence of an SGLT protein. The lack of clear pattern may be attributable to a lack of antibody specificity as they were generated against mammalian SGLTs. Similar results have been reported for several species of fish.