Effect of protein kinase C modulators on the leucocyte Na+/H+ antiport in type 1 (insulin-dependent) diabetic subjects with albuminuria

• Published in: Diabetologia Vol. 33; no. 5; p. 278
• Main Authors: Ng, L L, Simmons, D, Frighi, V, Garrido, M C, Bomford, J
• Format: Journal Article
• Language: English
• Published: Germany 01.05.1990
• Subjects: Albuminuria; Alkaloids - pharmacology; Amiloride - analogs & derivatives; Amiloride - pharmacology; Blood Glucose - analysis; Carrier Proteins - blood; Diabetes Mellitus, Type 1 - blood; Diabetes Mellitus, Type 1 - urine; Diabetic Nephropathies - blood; Glycated Hemoglobin A - analysis; Humans; Hydrogen-Ion Concentration; In Vitro Techniques; Insulin - blood; Kinetics; Leukocytes - drug effects; Leukocytes - metabolism; Protein Kinase C - antagonists & inhibitors; Sodium-Hydrogen Exchangers; Staurosporine
• ISSN: 0012-186X
• DOI: 10.1007/BF00403321

It is uncertain why only one third of Type 1 (insulin-dependent) diabetic patients develop nephropathy. One suggestion is the inheritance of a predisposition to essential hypertension. We have previously found elevated Na+/H+ antiport activity and a raised intracellular pH in leucocytes from hypertensive and Type 1 diabetic subjects with albuminuria using a novel double ionophore fluorimetric technique. These changes are not found in Type 1 diabetic subjects without albuminuria. We wished to test the effect of a protein kinase C inhibitor staurosporine (100 nmol/l) on the elevated antiport activity, and the degree of stimulation achieved by exogenous diacyl glycerol. Raised leucocyte Na+/H+ antiport activity of Type 1 diabetic subjects with albuminuria (73.8 +/- 17.2 mmol.l-1.min-1) was restored to normal levels with staurosporine (54.9 +/- 17.9 mmol.l-1.min-1, p less than 0.001). The leucocyte Na+/H+ antiport activity of diabetic subjects without albuminuria fell significantly also with staurosporine but to a lesser extent (57.3 +/- 11.6 to 50.0 +/- 12.8 mmol/l, p less than 0.003). In contrast, leucocytes from normal control subjects showed no change in antiport activity with staurosporine (54.3 +/- 8.5 to 52.6 +/- 10.4 mmol.l-1.min-1). Dioctanoyl glycerol stimulated the leucocyte Na+/H+ antiport in normal subjects and diabetic patients without albuminuria, with significantly less stimulation in diabetic patients with albuminuria. We conclude that reversal by staurosporine of the elevated Na+/H+ antiport activity in Type 1 diabetic subjects with albuminuria could indicate a role for protein kinase C in activating the antiport. This hypothesis is supported by the reduced stimulation of the antiport by dioctanoyl glycerol in this group of patients.