• Grandy, David (PI)

    Project: Research project

    Project Details


    In addition to its importance as a neurotransmitter, dopamine has
    profound effects on heart rate, blood pressure, renal blood flow, sodium
    absorption and water retention. In the clinical setting dopamine is used
    to treat patients suffering from shock or impaired renal function. At
    low doses the renal effects of dopamine predominate and are mediated by
    two receptor subtypes: DA1 and DA2. Little is known about renal DA2
    receptor physiology. In contrast, DA1 dopamine receptors mediate
    natriuresis and diuresis in the tubules of the renal cortex and
    vasodilation of the mesenteric and renal vascular beds. DA1 receptors
    in proximal convoluted tubule (PCT) epithelial cells couple to the
    stimulation of cAMP and diacylglycerol (DAG) production. Increases in
    the concentration of these two second messengers activate protein kinases
    A and C, respectively. Two targets of these kinases are the luminal
    Na+/H+ exchanger (NHE) and the basolateral Na+-K+ATPase. Both the NHE
    and the ATPase are involved in sodium transport but it is the
    phosphorylation and subsequent inhibition of Na+/H+ exchanger activity
    that results in sodium excretion (natriuresis). Our results suggest that
    the dopamine D5 receptor that we recently cloned is identical to the
    renal PCT DA1 receptor subtype. We propose that dopamine D5 receptors
    in the renal PCT epithelia couple to second messenger systems that
    participate in the regulation of Na+/H+ exchanger activity. Therefore,
    any interference with the ability of D5/Da1 receptor's to regulate sodium
    transport may play an important role in the etiology of certain forms of
    essential hypertension. We propose to test several aspects of this
    hypothesis. Recently we demonstrated that activated dopamine D5
    receptors stimulate cAMP production and the secretion of H+. This latter
    effect is sensitive to amiloride suggesting that a Na+/H+ exchanger (NHE)
    activity is involved. We propose to pursue the in vitro characterization
    of D5's coupling to adenylyl cyclase and phospholipase C. In addition,
    we have the opportunity to develop a very powerful in vitro system in
    which to dissect D5's regulation of NHE activity. Cell lines expressing
    each of the three recently cloned NHEs and the D5 receptor will be
    evaluated with respect to dopaminergic regulation of sodium transport.
    We also have evidence to suggest that recombinant vaccinia virus vectors
    can be used to generate polyclonal anti-receptor antiserum. We will use
    this technology to produce anti-D5 antiserum, a valuable reagent for the
    analysis of dopamine D5 receptor expression and post translational
    modification in normal and diseased renal cortex tissue. Abnormal renal
    responses to dopamine have also been reported in two well-documented rat
    models of inherited hypertension and we are now in a unique position to
    determine whether the genetic defect lies within the dopamine D5 receptor
    gene. finally we intend to generate transgenic mice that lack functional
    dopamine D5 receptors. The production of these "knockout" mice will
    provide a new and powerful mouse model system in which the role of
    dopamine D5 receptors in renal physiology in general, and sodium
    transport in particular, can be evaluated.
    Effective start/end date8/1/937/31/98


    • National Institutes of Health: $102,317.00
    • National Institutes of Health: $103,658.00


    • Medicine(all)


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