The aim of this investigation was to study the effects of isoglycaemic hype
rinsulinaemia on the renal metabolism of electrolytes and water in subjects
with a strong genetic predisposition to essential hypertension, compared w
ith that in non-predisposed subjects. We studied 25 normotensive subjects a
ged 18-35 years whose parents both had essential hypertension, and 22 age-
and sex-matched subjects whose parents were both normotensive. Diabetes or
morbid obesity in any subject or parent excluded the family. The 24-h blood
pressure was measured. The subjects received an isocaloric diet with a fix
ed content of sodium and potassium for 4 days before the study. An isoglyca
emic, hyperinsulinaemic clamp with infusion of insulin (40 munits.min(-1).m
(-2)) was performed. We measured the renal clearance of diethylenetriamine-
penta-acetic acid, sodium, potassium and lithium both under basal condition
s and during hyperinsulinaemia. In response to hyperinsulinaemia, renal sod
ium clearance decreased to a significantly greater extent in the hypertensi
on-prone subjects [0.57 (0.74, 0.36) ml.min(-1).1.73 m(2) (median and quart
iles)] than in the controls [0.34 (0.56, 0.18) ml.min(-1).1.73 m(2)] (P = 0
.04). Compared with the controls, the subjects predisposed to hypertension
had a higher 24-h diastolic blood pressure [78 (70, 82) mmHg, compared with
73 (68, 77) mmHg], but a similar insulin sensitivity index {10(7) x [313 (
225, 427)] compared with 10(7) x [354 (218, 435)] I-2.min(-1).pmol(-1).kg(-
1)}. Thus the sodium-retaining effect of insulin was more pronounced in sub
jects with a strong genetic predisposition to essential hypertension than i
n subjects with normotensive parents. This effect may contribute to the dev
elopment of hypertension in subjects with a genetic predisposition to hyper
tension.