Role of cyclooxygenase in the vascular responses to extremity cooling in Caucasian and African males

African descent (AFD) individuals are more susceptible to non-freezing cold injury (NFCI) and experience an exaggerated cutaneous vasoconstrictor response to hand cooling compared with Caucasians (CAU). Using a placebo-controlled, crossover design, this study tested the hypothesis that cyclooxygenase (COX) may, in part, be responsible for the exaggerated vasoconstrictor response to local cooling in AFD. Twelve AFD and twelve CAU young healthy males completed foot cooling and hand cooling (separately, in 8°C water for 30 minutes) with spontaneous rewarming in 30°C air following placebo or aspirin (COX inhibition) treatment. Skin blood flow, expressed as cutaneous vascular conductance (CVC, flux•mmHg⁻¹), and skin temperature (Tsk) were measured throughout. Irrespective of COX inhibition, the responses to foot cooling, but not hand cooling, were similar between ethnicities. Specifically, during hand cooling following placebo, AFD experienced a lower minimum skin blood flow (0.5 [0.1] vs. 0.8 [0.2] flux•mmHg⁻¹, P < 0.001) and a lower minimum finger T_sk (9.5 [1.4]°C vs. 10.7 [1.3]°C, P = 0.039) compared with CAU. During spontaneous rewarming average skin blood flow was also lower in AFD than CAU (2.8 [1.6] vs. 4.3 [1.0] flux•mmHg⁻¹, P < 0.001). These data provide further support that AFD experience an exaggerated response to hand cooling and thus NFCI; however, the results demonstrate the COX pathway is not the primary reason for the exaggerated responses in AFD and increased susceptibility to NFCI.