1.The aim of this study was to determine the effects of high (220 ;mmol/day) and low (40 ;mmol/day) salt intake for 6 days on blood pressure, leg blood flow and insulin sensitivity in 18 ;healthy normotensive subjects.
2.Twenty-four-hour ambulatory blood pressure was measured at baseline, during salt-loading and salt-depletion. Insulin sensitivity was determined by a two-step euglycaemic–hyperinsulinaemic clamp (low and high insulin infusion rates: 40 and 600 ;m-unit·min-1·m-2 respectively) and leg blood flow by plethysmography.
3.Salt-loading resulted in changes in weight [change between salt-loading and salt-restriction: δ =+0.45 (S.D.±0.69) ;kg, P = 0.015], plasma renin [δ =-11.5 (S.D.±12.9) ;μ-units/l, P = 0.001] and urinary noradrenaline [δ =-8.6 (S.D.±18.7) ;nmol/mmol creatinine, P = 0.05]. There were borderline significant increases in 24-h systolic blood pressure [δ =+5.8 (S.D.±14.2) mmHg, P = 0.06] and plasma volume [δ =+0.29 (S.D.±0.67) litres, P = 0.08].
4.Insulin sensitivity was similar in both salt states. Geometric mean metabolic clearance rate of low-dose insulin: low salt, 5.13 (S.D.×/÷1.35) dl/min; high salt, 4.94 (S.D.×/÷1.37) dl/min, P = 1.0. Geometric mean metabolic clearance rate of high-dose insulin: low salt, 9.68 ;dl/min (S.D.×/÷1.30); high salt, 9.68 (S.D.×/÷1.27) dl/min, P = 0.69.
5.Leg blood flow response to high-dose insulin on high salt increased significantly compared with low salt. Percentage change of blood flow on low salt, δ =+36.6 (S.D.±22.9)% versus high salt, δ =+66.8 (S.D.±52.2)%, P = 0.03.
6.There were no significant relationships between salt-related changes in limb blood flow and changes in insulin sensitivity at either insulin infusion rate.
7.We conclude that salt-loading, despite changing body weight, the renin–angiotensin–aldosterone system, urinary noradrenaline and the leg blood flow response to insulin, has no significant effect on insulin sensitivity. Salt-loading causes dissociated effects on insulin-induced vasodilatation and glucose disposal.