Abstract
Objective. The goals of the present study were (1) to examine ethnic differences in cardiovascular reactivity to the evaluative speech stressor between black and white men; (2) to assess ethnic differences in pressor responses to isoproterenol and phenylephrine challenges, as indexes of beta- and alpha-adrenoceptor responsivity; and (3) to determine whether the ethnic differences in stress reactivity can be accounted for by the differential patterns of adrenergic receptor responsivity between blacks and whites. Methods. Hemodynamic responses to an evaluative speech task and bolus intravenous injections of isoproterenol and phenylephrine were evaluated in forty-nine normotensive men (24 blacks and 25 whites) aged 18--25. Results. Comparisons of ethnic differences in cardiovascular reactivity revealed that whites exhibited significantly greater increases in SBP, CO, and HI relative to blacks. For the assessment of adrenergic function, ethnic differences in cardiovascular responses were evaluated at the effective dose of isoproterenol (1.0 mug) and phenylephrine (200 mug). The effective dose was determined as the lowest dose of adrenergic agent yielding group differences in pressor responses. The data indicated that whites showed greater increases CO and HI to the effective dose of isoproterenol compared to blacks. Ethnic differences in response to the effective dose of phenylephrine were also detected with blacks exhibiting a greater decrease in CO, smaller increase in SV, and larger increase in TPR relative to whites. To evaluate whether the ethnic differences in DeltaSBP, DeltaCO, and DeltaHI to the stressor can be accounted for by peripheral adrenoceptor responsivity, correlation analyses were performed. The analyses did not yield significant associations between DeltaSBP, DeltaCO, and DeltaHI to the speech task and the adrenergic agonists. Conclusions. The findings indicate that the pressor reactivity to the speech task parallel that of responses to the adrenergic agonists in healthy black and white men. However, despite a similar pattern of responses, an association between stress reactivity and adrenergic responsivity was not observed. This preliminary evidence suggests that the pattern of hemodynamic reactivity elicited by challenge between blacks and whites may not be related to peripheral receptor responsivity.