Urinary kallikrein excretion is low in malignant essential hypertension

To determine whether the urinary excretion of kallikrein is altered in patients with previously malignant hypertension.

Twenty-two patients with malignant hypertension (fundus hypertonicus III or IV) in the Gothenburg area were studied over a 3-year period. After treatment had begun they were investigated for blood pressure control, family history of hypertension, renal function and urinary kallikrein and plasma prekallikrein concentrations. Twenty-two patients with treated non-malignant hypertension and 36 control subjects were investigated concomitantly. The two hypertensive groups were also separated into subgroups of essential and secondary hypertension.

Prekallikrein was activated and kallikrein determined by a spectrophotometric assay using a synthetic chromogenic substrate. Renal function was estimated by serum creatinine and 51Cr-ethylenediaminetetraacetic acid clearance.

Prekallikrein levels tended to be elevated in all groups of hypertensive patients compared with controls whilst urinary kallikrein was significantly decreased in malignant hypertensives. The most pronounced suppression of urinary kallikrein was seen in the group of patients with essential malignant hypertension. The differences persisted when urinary kallikrein was related to the degree of renal impairment or when urinary volume was taken into account. There was no relation between family history of hypertension and low levels of urinary kallikrein.

Decreased urinary kallikrein could indicate depressed activity in the renal kallikrein-kinin system, which may be associated with the initiation of essential malignant hypertension.