Abstract-The efficacy and tolerability of eplerenone, a selective aldosterone blocker, was assessed when added to existing antihypertensive therapy with an ACE inhibitor or an angiotensin II receptor blocker (ARB). Hypertensive patients (nϭ341) whose blood pressure (BP) was not controlled despite ACE inhibitor or ARB were randomized (double-blind) to receive 50 mg eplerenone (increasing to 100 mg if required) once daily or placebo for 8 weeks.

It has been reported that kinins mediate part of the beneficial cardiac effects induced by treatment with angiotensin-converting enzyme inhibitors in situations such as ischemia-reperfusion injury, myocardial infarction, and cardiac hypertrophy. However, it is not known whether the heart contains an independent kallikrein-kinin system. We measured kallikrein in tissue and in the incubation medium of heart slices. Heart slices released active and total (trypsinactivatable) kallikrein into the medium (46±5 and 380±18 pg bradykinin/mg, respectively, after 1 hour and 78±6 and 654±14 pg bradykinin/mg after 2 hours, n=7). Release was not due to tissue damage because lactate dehydrogenase, a cytosolic marker, decreased from 8.9±2.9 to 2.9±1.0 U/mg per hour. Although kallikrein was released, total tissue kallikrein in the slices did not change (423 ±25 pg bradykinin/mg in nonincubated slices and 370±42 pg bradykinin/mg after 2 hours, / > =NS), suggesting pool replenishment. Cardiac kallikrein activity was inhibited by incubation with anti-glandular

A kininogenase resembling glandular kallikrein was partially purified from vascular tissue and characterized. Saline-perfused rat tail arteries and veins were homogenized in 0.25 M sucrose containing 10 mM Tris-HCl (pH 7.4). The homogenate was centrifuged at 105,000 g for 60 minutes, and a vascular kininogenase was purified from the supernatant by chromatofocusing, affinity chromatography on immobilized antibodies against rat urinary kallikrein, and gel filtration on Sephadex G-100. The inhibitory effects of antibodies against rat urinary kallikrein were tested with equivalent kinin-forming concentrations of rat urinary kallikrein and vascular kininogenase. Kininogenase activities of both enzymes were similarly inhibited by both polyclonal and monoclonal antibodies. Aprotinin (1,000 KIU) completely inhibited vascular kininogenase activity, while soybean trypsin inhibitor (100 micrograms) did not modify its kinin-forming activity. Vascular kininogenase and rat urinary kallikrein had the same elution volume when chromatographed on a Sephadex G-100 column, and had similar mobilities in 10% polyacrylamide gel electrophoresis. Kinins released by vascular kininogenase were identified as bradykinin by reverse-phase high performance liquid chromatography. Rat vascular kininogenase appears to be similar to glandular kallikrein. Kinins released locally by vascular kininogenase may contribute to the regulation of vascular tone.

Vascular tissue contains kallikrein and kallikrein mRNA, suggesting a vascular kallikrein-kinin system. We questioned whether 1) kallikrein concentration varies among large and small vessels; 2) kallikrein is released by vascular tissue; and 3) blocking protein synthesis inhibits release, suggesting de novo synthesis. Using rat vascular rings and isolated-perfused hindquarters, we examined kallikrein in the bath and perfusate. Active kallikrein was higher in tail arteries than the aorta (P < 0.001); tail veins had six times more kininogenase than the vena cava (P < 0.001). Total kallikrein showed a similar pattern, being highest in tail vessels. Arterial rings released active and total kallikrein. After 1, 2, and 3 h incubation, cumulative release was as follows: active, 90 +/- 13, 201 +/- 25, and 311 +/- 41 pg.h-1 x mg tissue-1; total, 170 +/- 14, 366 +/- 24, and 537 +/- 40 pg.h-1 x mg tissue-1, indicating constant release up to > or = 3 h. In contrast, lactic dehydrogenase fell from 6.7 +/- 2.5 to 2.5 +/- 0.4 U.h-1 x mg tissue-1. Total kallikrein in the rings was 302 +/- 51 pg bradykinin/mg wt tissue before 3 h and 298 +/- 68 afterward. Kallikrein released by the hindquarters after 3 h was as follows: active, 6.2 +/- 2.8 ng bradykinin.min-1 x kg.body wt-1; total, 85.2 +/- 17 ng bradykinin.min-1 x kg body wt-1. Puromycin pretreatment (10 mg ip) reduced total perfusate kallikrein from 105 +/- 19 to 8.5 +/- 3.6 (P < 0.005).(ABSTRACT TRUNCATED AT 250 WORDS)

We studied whether the components of the kallikrein-kinin system are present in the central nervous system. We found that human cerebrospinal fluid (CSF) contains free kinins: 53 +/- 15 pg/ml; kininogen: 10.9 +/- 2.1 ng kinin equivalent/ml, and kininogenase activity: 5.0 +/- 2.1 ng kinins/ml/minute. Kininogenase activity was 2-3 fold augmented by preincubation with trypsin. Soybean trypsin inhibitor completely inhibited untreated CSF and partially inhibited trypsin activated kininogenase. Kininogenase activity and immunoreactive glandular kallikrein were present in rat brain, and their concentrations in hypothalamus is several-fold higher than in cortex, pons-medulla, basal ganglia and cerebellum. In the hypophysis, activity in pars-intermedia was between 6- and 20-fold higher than in posterior and anterior hypophysis, respectively. High activity was also found in the pineal gland. The kallikrein-kinin system is present in the central nervous system where it may participate in modulation of nervous and neuroendocrine functions.