1. Leucocyte Na+ influx in media containing 10 mmol/l Na+ was studied directly using a triple-isotope method for measuring initial 22Na uptake rates in 20 normal and 18 untreated hypertensive subjects. The effects of 1 mmol/l amiloride (a Na+-H+-antiport inhibitor) and 0.1 mmol/l bumetanide (a Na+, K+, Cl−-symport inhibitor) were also examined.
2. The total, amiloride-sensitive and bumetanide-sensitive influx rates were raised in hypertensive compared with normotensive subjects [median (range): total 0.63 (0.25–1.82) vs 0.40 (0.09–0.65) mmol min−1 l−1, P < 0.002; amiloride-sensitive 0.43 (0.18–1.56) vs 0.26 (0.04–0.48) mmol min−1 l−1, P < 0.002; bumetanide-sensitive 0.12 (−0.03 to 0.83) vs 0.02 (−0.25 to 0.21) mmol min−1 l−1, P < 0.005].
3. We conclude that hypertensive patients have a raised leucocyte total Na+ influx when measured in media containing 10 mmol/l Na+ and that this is contributed mainly by amiloride-sensitive and bumetanide-sensitive Na+ influx mechanisms.