Possible locus on chromosome 18q influencing postural systolic blood pressure changes

We conducted a genome-wide scan for quantitative trait loci influencing the systolic blood pressure, diastolic blood pressure, and pulse responses to a postural challenge in 498 white sibling-pairs from the Hypertension Genet ic Epidemiology Network, a multicenter study of the genetic susceptibility to hypertension. All participants were hypertensive (systolic blood pressur e greater than or equal to 140 mm Hg, diastolic blood pressure greater than or equal to 90 mm Hg, or on antihypertensive medications) with diagnosis b efore age 60. Blood pressure and pulse were measured by an oscillometric me thod after a 5-minute rest in a supine position and again immediately on st anding. The genome scan included a total of 387 autosomal short-tandem-repe at polymorphisms typed by the National Heart, Lung, and Blood Institute Mam malian Genotyping Service at Marshfield, We used multipoint variance-compon ents linkage analysis to identify possible quantitative trait loci influenc ing postural change phenotypes after adjusting for sex, age, and use of ant ihypertensive medications. There was suggestive evidence for linkage on chr omosome 18q for the postural systolic blood pressure response (maximum loga rithm of the odds score=2.6 at 80 centiMorgans). We also observed a maximum logarithm of the odds score of 1.9 for the systolic blood pressure respons e and 1.7 for the diastolic blood pressure response on chromosome 6p, The m arker that demonstrated the strongest evidence for linkage for the systolic blood pressure response (D18S858) lies within 20 centiMorgans of a marker previously linked to rare familial orthostatic hypotensive syndrome. Our fi ndings indicate that there may be 1 or more genes on chromosome 18q that re gulate systolic blood pressure during the physiological recovery period aft er a postural stressor.