Blunted blood pressure response to central sympathoinhibition in normotensive blacks: increased importance of nonsympathetic factors in blood pressure maintenance in blacks

Chim C. Lang, C. Michael Stein, Huai B. He, Frank J. Belas, Ian A. Blair, Margaret Wood, Alastair J. J. Wood

    Research output: Contribution to journalArticle

    31 Citations (Scopus)

    Abstract

    Enhanced sympathetic reactivity may predispose blacks to the development of hypertension and may occur because of increased sympathetic stimulation and/or attenuated sympathoinhibition. A potential site for such attenuated sympathetic inhibition may be at the level of central a2-adrenergic receptors, which play an important role in the feedback inhibition of norepinephrine release. We used cumulative doses (1, 2, and 3 µg/kg IV) of the centrally acting a2-adrenergic agonist clonidine to measure the sensitivity of a2-adrenoceptor–mediated sympathoinhibition and the resultant hypotensive response in 8 normotensive blacks and 10 normotensive whites. Sympathetic activity was determined by radioisotope dilution methodology. Basal norepinephrine spillover was similar in blacks (0.80±0.14 µg/min) and whites (0.73±0.19 µg/min, P=NS) and after clonidine decreased significantly in both blacks (0.21±0.07 µg/min, P<.0001) and whites (0.24±0.06 µg/min, P<.0001), with no difference between the groups (P=NS). Despite this similar degree of sympathoinhibition, the hypotensive response to clonidine was markedly blunted in blacks, such that mean arterial pressure decreased by only 10% in blacks but by 21% in whites (P<.0001). The smaller blood pressure decrement after clonidine in normotensive blacks, in the face of an equal degree of sympathoinhibition, suggests that even when sympathetic tone is decreased to the same level in blacks and whites, normotensive blacks have less reduction in blood pressure than whites, implying that nonadrenergic mechanisms contribute more to blood pressure maintenance in blacks than whites. Whether a similar  interethnic difference in response to sympathoinhibition occurs in hypertensive patients is as yet unknown.

    Original languageEnglish
    Pages (from-to)157-162
    Number of pages6
    JournalHypertension
    Volume30
    Issue number2
    DOIs
    Publication statusPublished - 1997

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    Maintenance
    Blood Pressure
    Clonidine
    Norepinephrine
    Adrenergic Agonists
    Radioisotopes
    Adrenergic Receptors
    Arterial Pressure
    Hypertension

    Cite this

    Lang, Chim C. ; Stein, C. Michael ; He, Huai B. ; Belas, Frank J. ; Blair, Ian A. ; Wood, Margaret ; Wood, Alastair J. J. / Blunted blood pressure response to central sympathoinhibition in normotensive blacks : increased importance of nonsympathetic factors in blood pressure maintenance in blacks. In: Hypertension. 1997 ; Vol. 30, No. 2. pp. 157-162.
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    title = "Blunted blood pressure response to central sympathoinhibition in normotensive blacks: increased importance of nonsympathetic factors in blood pressure maintenance in blacks",
    abstract = "Enhanced sympathetic reactivity may predispose blacks to the development of hypertension and may occur because of increased sympathetic stimulation and/or attenuated sympathoinhibition. A potential site for such attenuated sympathetic inhibition may be at the level of central a2-adrenergic receptors, which play an important role in the feedback inhibition of norepinephrine release. We used cumulative doses (1, 2, and 3 µg/kg IV) of the centrally acting a2-adrenergic agonist clonidine to measure the sensitivity of a2-adrenoceptor–mediated sympathoinhibition and the resultant hypotensive response in 8 normotensive blacks and 10 normotensive whites. Sympathetic activity was determined by radioisotope dilution methodology. Basal norepinephrine spillover was similar in blacks (0.80±0.14 µg/min) and whites (0.73±0.19 µg/min, P=NS) and after clonidine decreased significantly in both blacks (0.21±0.07 µg/min, P<.0001) and whites (0.24±0.06 µg/min, P<.0001), with no difference between the groups (P=NS). Despite this similar degree of sympathoinhibition, the hypotensive response to clonidine was markedly blunted in blacks, such that mean arterial pressure decreased by only 10{\%} in blacks but by 21{\%} in whites (P<.0001). The smaller blood pressure decrement after clonidine in normotensive blacks, in the face of an equal degree of sympathoinhibition, suggests that even when sympathetic tone is decreased to the same level in blacks and whites, normotensive blacks have less reduction in blood pressure than whites, implying that nonadrenergic mechanisms contribute more to blood pressure maintenance in blacks than whites. Whether a similar  interethnic difference in response to sympathoinhibition occurs in hypertensive patients is as yet unknown.",
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    Blunted blood pressure response to central sympathoinhibition in normotensive blacks : increased importance of nonsympathetic factors in blood pressure maintenance in blacks. / Lang, Chim C.; Stein, C. Michael; He, Huai B.; Belas, Frank J.; Blair, Ian A.; Wood, Margaret; Wood, Alastair J. J.

    In: Hypertension, Vol. 30, No. 2, 1997, p. 157-162.

    Research output: Contribution to journalArticle

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    T2 - increased importance of nonsympathetic factors in blood pressure maintenance in blacks

    AU - Lang, Chim C.

    AU - Stein, C. Michael

    AU - He, Huai B.

    AU - Belas, Frank J.

    AU - Blair, Ian A.

    AU - Wood, Margaret

    AU - Wood, Alastair J. J.

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