Beta-blockers and aldosterone antagonists have the strongest impact on the renin-angiotensin system. The decrease in renin concentration by beta-blockers leads to an increase in the ratio of aldosterone to renin, and thus to false-positive results in patients with essential hypertension. Calcium channel blockers, and probably also ACE inhibitors and AT1 receptor antagonists alone or in combination, may be continued during screening for primary aldosteronism by determination of renin and aldosterone concentration.

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The ratio of serum aldosterone to plasma renin activity (PRA) has been proposed as sensitive screening method in the diagnosis of primary aldosteronism under random conditions. However, the method for determination of renin activity is hampered by the necessity of ice cooling during storage and transport. The present study was therefore conducted to examine the ratio of serum aldosterone to plasma renin concentration (ARR) and its usefulness in diagnosis of primary aldosteronism under ambulatory conditions and given antihypertensive medication. 146 patients with arterial hypertension who consecutively attended the outpatient clinic were studied prospectively. Patients with secondary hypertension besides primary aldosteronism were not included in the series. 37 normotensive patients served as control. Also, 17 patients with known primary aldosteronism were retrospectively examined. Among the hypertensive group 2 patients with Conn's syndrome were newly detected (1.4%). ARR was 7.92 +/- 6.04 [pg/ml]/[pg/ml] in normotensive controls (range from 2.03 to 26.98), 14.61 +/- 18.50 [pg/ml]/[pg/ml] in patients with essential hypertension (n = 144, range from 0.41 to 115.45) and 155.92 +/- 127.84 [pg/ml]/[pg/ml] in patients with primary aldosteronism (n = 19, range from 6.75 to 515). 17 of the 19 patients with Conn's syndrome had an ARR of more than 50. Under ongoing drug treatment this represents a sensitivity of 89% and a specificity of 96%. Sensitivity decreased to 84% and specificity increased to 100% when a second criteria (aldosterone > or = 200 pg/ml) was included. In summary, ARR using renin concentration is a useful screening parameter for primary aldosteronism.

Histamine exhibits various biological effects in inflammatory and immunological reactions. To further define its potential role in allergic enteropathy and inflammatory bowel disease, both gut mucosal histamine levels and histamine release from endoscopic biopsy samples were measured. Tissue histamine content resulted from addition of the released amount of histamine and the remaining part of tissue histamine. The results demonstrate highly elevated mucosal histamine levels of the large intestine in allergic enteropathy. In inflammatory bowel disease histamine content and secretion were found to be significantly increased particularly in affected mucosa of Crohn’s disease and ulcerative colitis than in unaffected tissue or in healthy controls. These findings give strong evidence that mast cell mediators like histamine play a role in the pathogenesis of these diseases. Mucosal histamine is thus concluded to contribute to the immunoinflammatory reactions of the intestine found in these disease states and to reflect the degree of colonic inflammation in Crohn’s disease and ulcerative colitis.

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