A study of the sodium‐glucose co‐transports of the avian kidney

Abstract

Given animals of similar body mass, birds have been shown to have much higher plasma glucose concentrations than that of mammals. However, birds appear not to show the pathological symptoms associated with high plasma glucose levels as seen in mammals. As the glomerular filtration rates (on a mass specific basis) of birds and mammals are not significantly different and with higher plasma glucose levels, birds must have a larger filtered load of glucose. Despite this there is little or no detectable glucose in the ureteral urine of birds. This suggests that the mechanisms for glucose reabsorption by the bird kidney must be significantly up-regulated. In mammals glucose reabsorption is achieved through the sodium-glucose co-transport proteins (SGLTs) located in the apical cell membrane of the proximal renal tubule. The putative SGLTs within the avian kidney have not been isolated or characterized. Using SDS-PAGE and Western blots, we have been able to demonstrate the present of an immuno-reactive protein in the kidneys from mourning doves albeit not at the same intensity as that the rat kidney used as control.