Aggregation of erythrocyte sodium/lithium countertransport activity in families of patients with immunoglobulin A nephropathy

Abstract

1. We evaluated the inheritance of erythrocyte Na+/Li+ countertransport activity in IgA nephropathy by assessing this parameter in 19 patients with biopsy-proven IgA nephropathy and in their 53 relatives (32 parents and 21 siblings). The possible use of erythrocyte Na+/Li+ countertransport activity as a marker of poor prognosis was also evaluated. 2. A significant correlation was found between 'familial' and proband Na+/Li+ countertransport activity, but not between that of spouses. 3. Mean blood pressure, although within the normal range, and Na+/Li+ countertransport activity were significantly higher in patients with proteinuria than in those without proteinuria. 4. Parents of proteinuric patients had a higher Na+/Li+ countertransport activity than parents of non-proteinuric patients. 5. In IgA nephropathy the inheritance of erythrocyte Na+/Li+ countertransport activity was preserved. Therefore genetic factors could play a role in the non-immunological progression of IgA nephropathy.

Raised Affinity for Extracellular Sodium of the Sodium-Lithium Countertransporter is Associated with a Family History of Hypertension and Uraemia in Patients with Renal Disease

“…In patients with renal impairment there have been reports of elevated standard SLC activity [l-41 and this has been associated with a familial predisposition to hypertension and cardiovascular disease [l-31. Similarly, elevated SLC activity was recently reported in hypertensive patients with IgA nephropathy [5,61 and this finding was related to a less favourable disease outcome [7,81. A genetic association of SLC activity with IgA nephropathy was suggested by the demonstration of elevated standard SLC activity in normotensive relatives of patients with IgA nephropathy [7].…”

“…Similarly, elevated SLC activity was recently reported in hypertensive patients with IgA nephropathy [5,61 and this finding was related to a less favourable disease outcome [7,81. A genetic association of SLC activity with IgA nephropathy was suggested by the demonstration of elevated standard SLC activity in normotensive relatives of patients with IgA nephropathy [7]. Taken together, these studies indicate that SLC activity could provide a useful marker of cardiovascular risk in renal patients; however, there are a number of conflicting studies that have indicated an unchanged SLC activity in renal disease .…”

Sodium-Lithium Countertransport Kinetics in IgA Nephropathy: Relation to Plasma Lipids and Renal Impairment

“…It seems likely that in IgA-NRF patients, standard SLC is increased in association with raised plasma lipids almost certainly operating through Vmax. This could also be the mechanism of the raised standard SLC activity found in the patients and the relatives of the patients with IgA nephropathy and proteinuria in the family study of SLC activity in IgA nephropathy by Fabbri et al [17], How ever, plasma lipids were not reported on the relatives, so this possibility requires clarification.…”

“…The previous studies of SLC in IgA nephropathy patients simply measured the standard activity [16,17] but suggested that familial factors were important in determining activity. We have performed a more rigor ous kinetic analysis of SLC activity in IgA nephropathy in patients with and without a raised creatinine.…”

Kinetic characteristics of the erythrocyte sodium-lithium countertransporter in black normotensive subjects compared with three other ethnic groups

“…The negative correlation between k Na and serum creatinine in the Caucasian subjects is of particular interest since elevated countertransport activity, which may incorporate reduced k Na , has been associated with impaired renal function in both diabetic 41,42 and non-diabetic subjects. 43,44 Perhaps it is more than a coincidence that reduced k Na values have been reported not only in hypertension and vascular disease 15,16 but also in the diabetic with overt nephropathy, 45 a condition which itself is associated with hypertension.…”