Abstract-Salt sensitivity (SS) has been linked to human hypertension. We examined ethnic differences in the relation between SS; erythrocyte sodium (Na ; and sodium pump activity in African-American (AA) and white women. In a crossover protocol, similar numbers of normotensive, hypertensive, AA, and white women were randomized to 7 days of a 20 meq/d and a Ͼ200 meq/d salt diet (nϭ199). After an overnight inpatient stay, group differences in supine blood pressure (BP), heart rate, erythrocyte cations, and sodium pump activity were measured. The prevalence of SS (53.5% vs 51%) and salt resistance (26.3% vs 30.0%) was similar in both races. Greater mean BP increase with salt loading was seen in AA vs white hypertensives but not between the normotensive women. In hypertensives, increase in mean arterial pressure was 12.6 vs 8.2 mm Hg in AAs vs whites, respectively (PϽ0.01), and for systolic BP, it was 23 vs 14.8 mm Hg (PϽ0.01). Higher Na i were positively correlated with salt responsiveness in AA but not in white women. Sodium pump activity was similar between groups, although the change in maximal activity trended to vary inversely with SS in AA. In closely matched AA and white women, the prevalence of SS is similarly high in both races, although the magnitude of BP increase is greater in AA hypertensives. In AA but not in whites, SS is positively associated with Na ssential hypertension continues to be a major cause of morbidity and mortality in industrialized populations of the world and one for which there is no known cause. In the United States, the prevalence of hypertension increases with age, and at about age 55, the prevalence becomes greater in women versus men. 1 More than half of white and three fourths of African-American (AA) women will develop hypertension by age 65 to 74 years. Acute blood pressure (BP) elevation with increasing salt intake (salt sensitivity [SS]) is commonly reported in large segments of the population, especially in those with renal disease, diabetes, obesity, hypertension, and older age and in AA. 2,3 BP sensitivity to salt might also predict chronic BP elevation, and normotensives with this trait are more likely to develop hypertension. 2,4 However, the pathophysiology of SS and its progression to hypertension remain poorly understood. This is further complicated by the significant heterogeneity in methods of defining SS. [5][6][7][8]20 Increased intracellular sodium ([Na ϩ ] i ,) assessed primarily in circulating blood cells, is one of the most consistently reported abnormalities of cation metabolism in essential hypertension, although a link between intracellular cation metabolism and salt-induced elevation of BP has not been established. A number of epidemiologic studies have documented a direct correlation between [Na ϩ ] i and BP in AA but not in non-AA. 9 -15 Racial differences in several membrane sodium-transport systems have also been reported. 14 -16 Na,KATPase (sodium pump) is a principal regulator of [Na ϩ ] i . Lower sodium pump activity has been reported in AA versus...

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This study characterizes the receptor binding and functional effects of 2R)-2-hydroxycyclopentyl)-amino]purin-9-yl}(4S,5S,2R,3R)-5-[(2-fluorophenylthio)methyl]-oxolane-3,4-diol], a novel N 6 -5Ј-substituted adenosine analog and A 1 -adenosine receptor (A 1 AdoR) agonist, on rat epididymal and inguinal adipocytes and on the isolated heart and compares these effects with those caused by the full agonist N 6 -cyclopentyladenosine (CPA). In addition, the hypothesis that adipocyte A 1 AdoR are a heterogeneous population with regard to their affinities for ligands was tested. CVT-3619 was 10 -100-fold selective for A 1 AdoR versus other AdoR and bound to adipocyte membranes with high (K H ϭ 14 nM) and low (K L ϭ 5.4 M) affinities. CVT-3619 reduced cyclic AMP content and release of nonesterified fatty acids from epididymal adipocytes with IC 50 values of 6 and 44 nM, respectively. CVT-3619 was a partial agonist relative to CPA to reduce lipolysis in epididymal and inguinal adipocytes. CVT-3619 did not change atrial rate in rat heart and caused a small (6-ms) prolongation of the stimulus-to-His bundle interval without causing atrioventricular block in guinea pig heart (effects mediated by A 1 AdoR), whereas CPA caused atrioventricular block and near cessation of atrial electrical activity. CVT-3619 increased coronary conductance (effect mediated by A 2A AdoR) only at concentrations Ն10 M. Rat epididymal adipocyte A 1 AdoR had similar affinities for the antagonist 8-cyclopentyl-1,3-dipropylxanthine in the presence of three dissimilar A 1 AdoR agonists (2-chloro-N 6 -cyclopentyladenosine, N 6 -sulfophenyladenosine, and N-5Ј-ethylcarboxamidoadenosine) as determined by Schild analysis. It was concluded that rat epididymal adipocyte A 1 AdoR are a homogeneous receptor population with regard to affinities for ligands and that CVT-3619 is a partial agonist with selectivity for A 1 AdoR and inhibition of lipolysis.

The secreted immunoglobulin footprint of single hybridoma cells, containing ~10 fg of antibody purified in situ, has been probed for 9 properties concurrently by use of detection labels comprising 280 nm combinatorially colored fluorescent latex beads functionalized with proteins. Specificity of each individual hybridoma cell's product has thereby been assessed in a primary screen. Varying the density of antigen on beads to modulate the avidity of the interaction between bead and secreted antibody footprint allowed rank ordering by affinity in the same primary screen. As more criteria were added to the selection process, the frequency of positive cells went down; in some cases, the favorable cell was present at <1/50,000. Recovery of the cell of interest was accomplished by plating the cells in a viscous medium on top of a membrane. After collecting the antibody footprint on a capture surface beneath the membrane, the immobilized cells were transferred to an incubator while the footprints were analyzed to locate the hybridoma cells of interest. The desired cells were then cloned by picking them from the corresponding locations on the membrane.