Abnormal urinary kallikrein in hypertension is not related to aldosterone or plasma renin activity

The relationships between urinary kallikrein (Ukal), and plasma renin activity (PRA), urinary aldosterone (Ualdo), Na+ balance, SK+, and renal function were studied in essential hypertensives (EHT) and normals. Ukal was measured by a radiochemical esterolytic assay. We studied 18 white patients with EHT (15 men, 3 women) ages 31.6 to +/- 2.1 (SEM) yrs, BP 138 +/- 2/95 +/- 2 mm Hg. and 12 white normals (NLS) (7 men, 5 women) ages 30.2 +/- 2.3 yrs, BP 112 +/- 4/71 +/- 2 mm Hg. All received a 5-day diet of 400 mEq Na+, 80 mEq K+/day, and 5 days of 10 mEq Na+, 80 mEq K+/day. All achieved Na+ balance by Day 5. On Day 5 of the low Na+ diet, 24 hr. Ukal in EHT was 15.8 +/- 2.4 (esterase units/24 hr) vs NLS, 17.0 +/- 2.8 PRA was the same in EHT and NLS, but Ualdo was higher in NLS. (Day 5, low Na+, EHT, Ualdo = 29.4 +/0 3.3 microgram/24h. vs NLS 41.8 +/- 4.7, p less than 0.02). Analysis of individuals showed that all NLS increased Ukal after salt restriction, while 3 EHT decreased Ukal after salt restriction. This abnormal response in EHT was not related to abnormalities in Ualdo, PRA, Na+ balance, SK+, or creatinine clearance. In 3 EHT with low-renin EHT, the Ukal response was normal. In two of four patients with primary aldosteronism, Ukal was normal despite increased Ualdo. The Ukal response to salt restriction is abnormal in some EHT, unrelated to Ualdo or PRA, suggesting either a primary defect in Ukal and/or the presence of other factors modulating Ukal in EHT.