OBJECTIVE To investigate the response of skin arterioles from control subjects and patients with scleroderma and Raynaud's phenomenon (RP/SSc) to cooling and modulators of protein tyrosine kinase (PTK) activity. METHODS We used the microvessel perfusion technique to characterize the response of isolated dermal arterioles (100-200 microm, outside diameter) from normal (n = 17) and RP/SSc (n = 17) subjects to cooling from 37 degrees to 31 degrees C. Fluorescent immunohistochemistry was used to measure tyrosine phosphorylation. RESULTS Arterioles from control subjects exhibited dilation in response to cooling from 37 to 31 degrees C whereas those from RP/SSc subjects contracted (+4.3 +/- 1.7 vs -16.7 +/- 3.1%, P < 0.05, n = 6). In the presence of the protein tyrosine phosphatase inhibitor sodium orthovanadate (SOV, 10 microM), the response of arterioles from control subjects did not change; however, arterioles from RP/SSC subjects exhibited a significantly greater contraction (-72.6 +/- 19.7%; P < 0.05, n = 6). Tyrosine phosphorylation of arterioles at 37 degrees C from control and RP/SSc subjects was similar. In response to cooling to 31 degrees C, however, arterioles from RP/SSc subjects exhibited a significantly greater increase in tyrosine phosphorylation compared with those from control subjects (43 +/- 7.0% vs 10 +/- 3.8%; P < 0.01). SOV increased tyrosine phosphorylation in arterioles from both groups (73 +/- 11.6% vs 42 +/- 5.6%; P < 0.05, n = 5). Arterioles from RP/SSC subjects precontracted with norepinephrine exhibited greatly attenuated relaxation to acetylcholine compared with those from control subjects. CONCLUSION The results of this study support the view that the hallmark of Raynaud's phenomenon associated with scleroderma, cooling-induced vasospasm, appears to be mediated by an increase in PTK activity possibly exacerbated by impaired endothelium-dependent vasodilation.