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Intracellular pH and sodium, proton antiport activity of cultured skin fibroblasts from diabetics

Intracellular pH and sodium, proton antiport activity of cultured skin fibroblasts from diabetics

Kidney International 42(5): 1184-1190

Increased leucocyte Na+/H+ antiport activity has previously been demonstrated in both hypertensive subjects and Type 1 diabetic patients with nephropathy and may indicate a predisposition to hypertension in such diabetic patients. We have studied intracellular pH and Na+/H+ antiport activity in cultured skin fibroblasts from diabetic patients with and without nephropathy, together with non-diabetic controls to assess if such differences persisted in cultured cells. Fibroblasts from diabetic patients with nephropathy were significantly more alkaline (median (range): 6.90 (6.82 to 7.07)) compared to both normoalbuminuric diabetic patients (6.81 (6.75 to 6.89)) or normal controls (6.82 (6.77 to 6.93)) (P lt 0.001 for both). This was associated with a raised Na+/H+ antiport activity in cells fro patients with nephropathy when intracellular pH (pH-i) was clamped to pH 6.5, without any differences in the maximal transport capacity of the antiport at pH-i 6.2. Using both intracellular pH and Na+/H+ antiport activity at pH-i 6.5, patients with nephropathy were separated from uncomplicated subjects with a sensitivity of 92% and a specificity of 100%. In conclusion, the raised Na+/H+ antiport activity in cells from patients with diabetic nephropathy persists despite passaging in vitro, thus indicating a heritable component, and results mainly from an increased apparent affinity of the antiport for intracellular H+.

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