Preventive roles of renal Kallikrein-kinin system for hypertension

大鼠尿液中的中性内切酶和羧基肽酶Y样激氨酶(CPY)可降解激动素，而血浆中的激动素II(ACE)主要失活。从放线菌中分离得到的依贝拉内酯B(EB)对大鼠尿液中的CPY有抑制作用，但对血浆中的激肽酶无抑制作用。血管紧张素转换酶抑制剂卡托普利显著抑制血浆激动素的降解。与同品系的正常大鼠(BN Kitasato(BN-KI)大鼠)相比，激肽原缺乏的Brown挪威Katholiek(BN-KA)大鼠的尿激肽排泄量可忽略不计。DOCA-盐处理使两个品系大鼠的全身血压(SBP)升高，但BN-KA缺陷大鼠的高血压发展速度比正常BN-KI大鼠快得多。每天皮下注射EB(5 mg/kg/d)3天后，BN-KI大鼠的平均SBP从117(SY+-)显著降低。[)3(n=5，车辆)至104()sy.+-。[)3毫米汞柱(n=5，EB)(p&lt；0.05)，但在BN-KA大鼠中不存在。这种治疗方式是…的显著增加BN-KI大鼠的尿钠排泄量，但不增加BN-KA大鼠的尿钠排泄量。血管紧张素转换酶抑制剂赖诺普利(5 mg/kg/day，S.C.)不能降低这两种类型的大鼠的SBP。经DOCA盐处理的BN-KI大鼠动脉激动素水平为-2.2(Sy.+-)。[]0.2pg/ml，但显著增加到4.6(Sy.+-)。[]0.4pg/ml+卡托普利(10 mg/kg，S.C.)。然而，静脉注射BK(1000 ng/kg/min)时引起低血压的动脉激肽水平。是卡托普利内源性动脉激肽水平的110倍。这些结果表明，抑制肾小管腔内侧激肽的降解可能有效地预防高血压。我们先前已报道，催产素(OT)是一种垂体激素，能够增加正常血压雄性SD大鼠尿中活性激肽释放酶的排泄。静脉输注钾(0.4mEq/kg/小时)也可增加尿激肽释放酶的排泄量。自发性高血压大鼠(SHR)断奶后即刻(4~6周龄)尿激肽释放酶排泄量明显低于Wistar京都大鼠(WKY)。在麻醉幼年(4周龄，雄性)SHR和WKY上，观察了催产素(OT)输注过程中活性激肽释放酶的排泄。催产素输注(30nmol/kg/30min)显著增加了WKY的活性激肽释放酶排泄量(25.4sy+-)。[)5.6AU/15分钟，n=5)至37.3(±)。[)5.0AU/15分钟(p&lt；0.05，n=5)和50.7([Sy.+-])。[]17.1AU/15分钟(p&lt；0.05，n=5)，分别于开始输注后15分钟和30分钟，但SHR组无明显变化，尿量和钠排泄量均下降。OT输注对上述两种类型大鼠的全身血压和尿肌酐排泄量均无影响。用双抗体夹心ELISA法测定，也不能改变WKY大鼠肾脏中活性激肽释放酶的组织浓度，但使SHR的活性激肽释放酶浓度略有升高。[30 ng/g/湿组织，n=8)超过WKY肾脏(560(]sy.+-)。[]50 ng/g湿组织，n=8)。在免疫组织化学研究中，SHR远端肾小管的激肽释放酶染色呈强阳性，提示在OT输注过程中，SHR尿激肽释放酶排泄减少可能与肾小管对激肽释放酶的敏感性降低有关。较少

Kinins were degraded by neutral endopeptidase and carboxypeptidase Y-like kininase (CPY) in rat urine, but were inactivated mainly by kininase II (angiotensin-converting enzyme, ACE) in rat plasma. Ebelactone B (EB), which was isolated from Actinomycetes, inhibited CPY in rat urine without inhibiting kininases in plasma. The ACE inhibitor captopril significantly inhibited the degradation of kinin in plasma. Kininogen-deficient Brown Norway Katholiek (BN-Ka) rats excreted a negligible amount of kinin in the urine, compared with normal rats from the same strain (BN Kitasato (BN-Ki) rats). DOCA-salt treatment increased systemic blood pressure (SBP) in both rat strains, but hypertension developed much faster in deficient BN-Ka rats than in normal BN-Ki rats. Daily subcutaneous administration of EB (5mg/kg/day) for 3 days significantly reduced mean SBP in the BN-Ki rats from 117(]SY.+-。[)3 (n=5, vehicle) to 104(]SY.+-。[)3 mmHg (n=5, EB) (p<0.05), but not in the BN-Ka rats. This treatment si … More gnificantly increased the urinary sodium excretion of the BN-Ki rats, but not of the BN-Ka rats. An ACE inhibitor, lisinopril (5mg/kg/day, s.c.), did not reduce the SBP in either type of rats. The arterial kinin levels in BN-Ki rats undergoing DOCA-salt treatment were-2.2(]SY.+-。[)0.2pg/ml, but were increased significantly to 4.6(]SY.+-。[)0.4pg/ml with captopril (10mg/kg, s.c.). However, the arterial kinin levels that induced hypotension on infusion of BK (1000ng/kg/min, i.v.) were 110 times the endogenous arterial kinin levels attained with captoprol. These results suggested that inhibition of kinin degradation on the luminal side of the renal tubules may effectively prevent hypertension.We have previously reported that one of the pituitary hormones, oxytocin (OT) has a capacity to increasee urinary excretion of active kallikrein in normotensive male Sprague-Dawley rats. Intravenous infusion of potassium (0.4 mEq/kg/hour) also increased the urinary excretion of active kallikrein. Urinary excretion of kallikrein in spontaneously hypertensive rats (SHR) was significantly less than that in Wistar Kyoto rats (WKY) immediately after weaning (4-6 weeks old). Excretion of active kallikrein during oxytocin (OT) infusion was studied in anesthetized young (4 weeks old, male) SHR and WKY.OT infusion (30 nmol/kg/30 min) significantly increased this excretion in WKY,from the basal levels (25.4(]SY.+-。[)5.6 AU/15 min, n=5) to 37.3(]SY.+-。[)5.0 AU/15 min (p<0.05, n=5) and 50.7(]SY.+-。[)17.1 AU/15 min (p<0.05, n=5) 15 and 30 min after the start of infusion, respectivey, but not in SHR.In SHR,urine volume and sodium excretion fell. The OT infusion did not change the systemic blood pressure or the urinary creatinine excretion in either typr of rats. It also failed to alter the tissue concentration of active kallikrein in the kidneys of WKY,as determined by a specific sandwich ELISA,but slightly increased those of SHR.After OT infusion, the concentrations of active kallikrein in SHR kidneys (770(]SY.+-。[)30 ng/g/ wet tissue, n=8) exceeded those in WKY kidneys (560(]SY.+-。[)50 ng/g wet tissue, n=8). In immunohistochemical studies, an intense kallikrein-positive stain was observed in the distal in the distal tubules in SHR.These results suggested that the lower excretion of urinary kallikrein in SHR during OT infusion may be attributable to diminished sensitivity in secretion of kallikrein from the renal tubules. Less