Insulin as a pressor agent: effects of 'physiological' insulin concentrations on finger blood pressure

Epidemiological evidence has linked essential hypertension with impaired tissue sensitivity to insulin (i.e. insulin resistance) and actions which could contribute to elevated blood pressure include renal sodium and water retention, sympathetic nervous system stimulation and effects on vascular smooth muscle cell growth and cation balance. Although insulin has pressor effects in some animal models, similar changes in human studies have only been demonstrable with supraphysiological insulin concentrations. We have recently measured finger blood pressure during a two stage hyperinsulinaemic euglycaemic clamp that produced insulin concentrations within the 'physiological' range. The plasma insulin concentration increased from 7.0 +/- 0.3 mu U.ml(-1) to 28.9 +/- 0.6 mu U.ml(-)and then to 101 +/-1.7 mu U.ml(-1) during the procedure and was associated with an increase in fingers but not arm systolic blood pressure during both low dose (i.e.+ 9.9 +/- 1.9 mmHg vs + 7.5 +/- 2.7 mmHg with control,p <0.05) and high dose insulin (21.9 +/- 2.3 mmHg vs 14.6 +/- 3.1 mmHg, p <0.01). Thus it appears that 'physiological' concentrations of insulin have pressor effects on finger systolic blood pressure that are not detectable more proximally and it is possible that such changes could contribute to the development of sustained elevations of blood pressure.