EFFECT OF MAGNESIUM-SULFATE INFUSION ON CIRCULATING LEVELS OF NORADRENALINE AND NEUROPEPTIDE-Y LIKE IMMUNOREACTIVITY IN PATIENTS WITH PRIMARY RAYNAUDS-PHENOMENON

The effect of a short-term magnesium sulfate (MgSO4) infusion on venou s plasma concentration of noradrenaline (NA) and neuropeptide-Y-like i mmunoreactivity (NPY-LI) was investigated in 12 women with primary Ray naud's phenomenon (PRP) and in 12 healthy matched controls. The Raynau d's patients did not demonstrate any significant changes in mean basal plasma NA concentration (0.29 +/-0.15 vs 0.37 +/-0.09 ng/mL, ns) afte r MgSO4 infusion. However, in the controls there was more than twice t he amount of circulating noradrenaline (cNA) (0.21 +/-0.14 vs 0.54 +/- 0.22 ng/mL, P < 0.001) after MgSO4 infusion, compared with the preinfu sion value. Measurements during the cold pressor test prior to the MgS O4 infusion showed a significant increase of cNA in both the PRP group and the control group (from 0.29 +/-0.15 to 0.33 +/-0.16 ng/mL, P < 0 .05, and from 0.21 +/-0.14 to 0.29 +/-0.16 ng/mL, P < 0.005, respectiv ely). After MgSO4 infusion the levels of cNA during the cold pressor t est increased significantly only in the PRP group (from 0.37 +/-0.09 t o 0.41 +/-0.11 ng/mL, P < 0.05). Circulating NPY-LI concentrations inc reased significantly during MgSO4 infusion in the Raynaud's patients a s well as in the controls from 105 +/-21 to 127 +/-23 pmol/L, P < 0.05 , and from 107 +/-17 to 132 +/-27 pmol/L, P < 0.01, respectively. Ther e were no detectable changes during the cold pressor tests in either g roup. In healthy women short-term MgSO4 infusion induced a sympathetic response, shown by the increased concentration of cNA and NPY-LI, whi le in PRP patients there was only an increase in NPY-LI. The discrepan cy between PRP patients and healthy controls supports the view of a so -called ''local fault'' in the sympathetic nerve terminal of arterial/ arteriolar walls in Raynaud's patients.