Comparison of vasodilator effects of substance P in human forearm vessels of normoalbuminuric Type 1 diabetic and non-diabetic subjects

Aims To compare the vasodilatory responses to substance P in human forearm vessels in Type 1 normoalbuminuric diabetic and non-diabetic subjects. Methods Forearm blood flow (FBF) was measured using a plethysmography techn ique in 12 normoalbuminuric Type 1 diabetic subjects (six males, six female s) (HbA(1c) 8.2 +/- 0.3% (mean +/- SEM)) and 12 non-diabetic healthy contro l subjects in response to the infusion of the vasodilators substance P (SP) , acetylcholine (ACh) and nitroprusside. Results There was no significant difference in baseline FBF between the two groups (2.80 +/- 0.29 ml/min per 100 ml forearm tissue (diabetic group) vs . 2.85 +/- 0.37 ml/min per 100 ml (non-diabetic group), P = 0.45). Infusion of SP was associated with an incremental increase in FBF in the diabetic ( 0.6, 2 and 6 ng/min - 6.08 +/- 1.07, 7.82 +/- 1.08 and 9.48 +/- 1.14 ml/min per 100 ml, respectively) and the non-diabetic group (0.6, 2 and 6 ng/min 5.41 +/- 0.80, 6.93 +/- 0.96 and 9.25 +/- 1.11 ml/min per 100 ml, respectiv ely). Similarly, an incremental rise in FBF was observed during infusion of ACh (diabetic group: 7.5, 15 and 30 mu g/min - 7.14 +/- 1.22, 8.91 +/- 1.4 0 and 11.67 +/- 1.93 ml/min per 100 ml, respectively; non-diabetic group: 7 .5, 15 and 30 mu g/min - 5.87 +/- 0.81, 7.49 +/- 0.96 and 10.74 +/- 1.29 ml /min per 100 mi, respectively). When FBF was expressed as percentage change from baseline, there was no significant difference in vasodilatory respons es between the two groups for SP (0.6 ng/min, P = 0.21; 2 ng/min, P = 0.19; 6 ng/min, P = 0.19) or ACh (7.5 mu g/min, P = 0.20; 15 mu g/min, P = 0.20; 30 mu g/min, P = 0.35). Conclusions This study suggests that endothelium-dependent vasodilatory res ponses to SP (and ACh) are not impaired in Type 1 diabetic subjects with no rmal urinary albumin excretion.