Clinical Investigation

Kidney International (1992) 42, 1184–1190; doi:10.1038/ki.1992.403

Intracellular pH and Na+/H+ antiport activity of cultured skin fibroblasts from diabetics

Joan E Davies, Leong L Ng, Allan Kofoed-Enevoldsen, Lai K Li, Ken A Earle, Roberto Trevisan and GianCarlo Viberti

Department of Pharmacology, Leicester Royal Infirmary, Leicester, England, United Kingdom; Steno Memorial Hospital, Gentofte, Denmark; and Unit for Metabolic Medicine, Guy's Hospital, London, England, United Kingdom

Correspondence: Dr L L Ng, Dept. of Pharmacology, Clinical Sciences Building, Leicester Royal Infirmary, Leicester LE2 7LX, United Kingdom.

Received 1 April 1992; Revised 9 June 1992; Accepted 16 June 1992.

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Abstract

Intracellular pH and Na+/H+ antiport activity of cultured skin fibroblasts from diabetics. 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 nondiabetic 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 < 0.001 for both). This was associated with a raised Na+/H+ antiport activity in cells from patients with nephropathy when intracellular pH (pHi) was clamped to pH 6.5, without any differences in the maximal transport capacity of the antiport at pHi 6.2. Using both intracellular pH and Na+/H+ antiport activity at pHi 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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References

  1. Krolewski AS, Warram JH, Christlieb AR, Bunsick EJ, Kahn CR: The changing natural history of nephropathy in type 1 diabetes. Am J Med 78:785–794, 1985 | Article | PubMed | ISI | ChemPort |
  2. Deckert T, Poulson JE: Diabetic nephropathy: Fault or destiny? Diabetologia 21:178–183, 1981
  3. Seaquist ER, Goetz FC, Rich S, Barbosa J: Familial clustering of diabetic kidney disease. N Engl J Med 320:1161–1165, 1989 | PubMed | ISI | ChemPort |
  4. Viberti GC, Keen H, Wiseman MJ: Raised arterial pressure in parents of proteinuric insulin dependent diabetics. Br Med J 295:515–517, 1987 | ISI | ChemPort |
  5. Krolewski AS, Canessa M, Warram JH, Laffel LMB, Christlieb AR, Knowler WC, Rand LI: Predisposition to hypertension and susceptibility to renal disease in insulin-dependent diabetes mellitus. N Engl J Med 318:140–145, 1988 | PubMed | ISI | ChemPort |
  6. Mangili R, Bending JJ, Scott G, Li LK, Gupta A, Viberti GC: Increased sodium-lithium countertransport activity in red cells of patients with insulin-dependent diabetes and nephropathy. N Engl J Med 318:146–150, 1988 | PubMed | ISI | ChemPort |
  7. Ng LL, Dudley C, Bomford J, Hawley D: Leucocyte intracellular pH and Na+/H+ antiport activity in human hypertension. J Hypertens 7:471–475, 1989
  8. Ng LL, Simmons D, Frighi V, Garrido MC, Bomford J, Hockaday TDR: Leucocyte Na+/H+ antiport activity in Type 1 (insulin-dependent) diabetic patients with nephropathy. Diabetologia 33:371–377, 1990 | Article | PubMed | ISI | ChemPort |
  9. Ng LL, Simmons D, Frighi V, Garrido MC, Bomford J: Effect of protein kinase C modulators on the leucocyte Na+/H+ antiport in Type 1 (insulin-dependent) diabetic subjects with albuminuria. Diabetologia 33:278–284, 1990
  10. Berk BC, Vallega G, Muslin AJ, Gordon HM, Canessa M, Alexander RW: Spontaneously hypertensive rat vascular smooth muscle cells in culture exhibit increased growth and Na+/H+ exchange. J Clin Invest 83:822–829, 1989 | PubMed | ISI | ChemPort |
  11. Davies JE, Ng LL, Ameen M, Syme PD, Aronson JK: Evidence for altered Na+/H+ antiport activity in cultured skeletal muscle cells and vascular smooth muscle cells of the spontaneously hypertensive rat. Clin Sci 80:509–516, 1991 | PubMed | ChemPort |
  12. Trevisan R, Li LK, Messent J, Tariq T, Earle KA, Walker JD, Viberti GC: Na+/H+ antiport activity and cell growth in cultured skin fibroblasts of diabetic patients with nephropathy. Diabetes (in press)
  13. Mason JM, Smith JD, Garcia-Soto JDJ, Grinstein S: Internal pH-sensitive site couples Cl--HCO-3 exchange to Na+/H+ antiport in lymphocytes. Am J Physiol 256 (Cell Physiol 25):C428–C433, 1989
  14. Bierman AJ, Cragoe EJ, de Laat SW, Moolenaar WH: Bicarbonate determines cytoplasmic pH and suppresses mitogen-induced alkalinization in fibroblastic cells. J Biol Chem 263:15253–15256, 1988
  15. Hogg M, Ng LL, Davies JE: Chloride influx in human leucocytes: A triple isotope technique for assessment of chloride transporters. Clin Sci 81:405–412, 1991
  16. Sardet C, Counillon L, Franchi A, Pouyssegur J: Growth factors induce phosphorylation of the Na+/H+ antiporter, a glycoprotein of 110 kD. Science 247:723–726, 1990 | PubMed | ISI | ChemPort |

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