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.