The autoradiographic diffusible tracer technique for the measurement of local cerebral blood flow was originally designed for use with the radioactive, inert gas 131I-labeled trifluoroiodomethane and is applicable only with tracers that exhibit unrestricted diffusion through the blood-brain barrier. Because of the technical problems associated with the use of gaseous tracers, a suitable nonvolatile tracer has been sought. [14C] Antipyrine has been used previously and found to be unsuitable because of limitations in its diffusion through the blood-brain barrier. An analogue of [14C]antipyrine, iodo [14C]antipyrine, exhibits higher partition coefficients than [14C]antipyrine between nonpolar solvents and water and might, therefore, be expected to diffuse more freely through the barrier. Its use as the tracer in the local blood flow technique leads to values considerably above those obtained with [14C]antipyrine in the rat and cat and essentially the same as those obtained with the gas trifluoro[131I]iodomethane in the cat. Iodo[14C]antipyrine appears, therefore, to be a satisfactory nonvolatile tracer for the measurement of local cerebral blood flow.

The bulk of glucose that is filtered by the renal glomerulus is reabsorbed by the glucose transporters of the proximal convoluted tubular epithelium. However, it has been difficult to investigate this in diseases such as type 2 diabetes because of the inability to isolate primary renal cells from patients without a renal biopsy. We report here a method for the immunomagnetic isolation and novel primary culture of human exfoliated proximal tubular epithelial cells (HEPTECs) from fresh urine. The primary isolates are highly enriched and differentiated and express characteristic proximal tubular phenotypic markers. They continue to express the proximal tubular markers CD13/aminopeptidase-N, sodium glucose cotransporter (SGLT) 2, and alkaline phosphatase through up to six subsequent subcultures in a similar way to human proximal cells isolated from renal biopsies. In a hyperglycemic environment, HEPTECs isolated from patients with type 2 diabetes expressed significantly more SGLT2 and the facilitative glucose transporter GLUT2 than cells from healthy individuals. We also demonstrated a markedly increased renal glucose uptake in HEPTECs isolated from patients with type 2 diabetes compared with healthy control subjects. Our findings indicate for the first time in a human cellular model that increased renal glucose transporter expression and activity is associated with type 2 diabetes. Diabetes 54:3427-3434, 2005

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