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

Abstract

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.

Inhibitory effect of ammonium chloride on acetylcholine-induced relaxation.

“…The maximal relaxation by acetylcholine (E^,, expressed as percentage of the level of norepinephrine-precontracted tension) and the acetylcholine concentration that produced a half-maximal relaxation (pD 2 …”

Glucose-induced changes in Na+/H+ antiport activity and gene expression in cultured vascular smooth muscle cells. Role of protein kinase C.

“…Of interest, many of the physical and functional abnormalities demonstrated in cell membranes from hypertensive patients, including Na+/H+ antiport activation, can be reproduced by the activation of PKC ( 11). With regard to diabetes mellitus, more recent studies have shown that the PKC inhibitor staurosporine can restore to normal the previously elevated leucocyte Na+/H+ antiport activity ofdiabetic patients, thereby suggesting that diabetes-induced increases in Na+/H+ antiport activity may be dependent on PKC activation (19). Diabetes mellitus is characterized by the development of hyperglycemia, and we have recently shown that elevated extracellular glucose concentrations (20 mM) induce a sustained activation of PKC in cultured VSMC (20,21 ).…”

Na+/Ca2+ exchange-mediated calcium entry in human lymphocytes.

“…In contrast to these observations, Donnadieu and co-workers (4,5) found no evidence of Na+/ examine this issue further, we have employed a sensitive assay to detect Na+/Ca2+ exchange activity in human lymphocytes, i.e., cytosolic Na+-dependent Ca2" influx. Identifying Na+/Ca2" exchange activity in lymphocytes would increase our understanding of functional alterations in cation transport in several pathological conditions. White blood cells from subjects exhibiting essential hypertension (6)(7)(8)(9) and diabetes mellitus (10,11) have been studied to gain insight into cellular Na+ and Ca2" transport abnormalities. However, in order for lymphocytes to serve as a model for cellular Na+ and Ca2" homeostasis, they should express the cation transport mechanisms found in the target cells known to be affected in these disorders.…”