A Taql RFLP at the human renal kallikrein (KLK1) locus

Activation of the renal kallikrein-kinin system results in natriuresis and diuresis, suggesting its possible role in renal tubular sodium transport regulation. Here, we used patch-clamp electrophysiology to directly assess the effects of bradykinin (BK) on the epithelial Na+ channel (ENaC) activity in freshly isolated split-opened murine aldosterone-sensitive distal nephrons (ASDNs). BK acutely inhibits ENaC activity by reducing channel open probability ( Po) in a dose-dependent and reversible manner. Inhibition of B2 receptors with icatibant (HOE-140) abolished BK actions on ENaC. In contrast, activation of B1 receptors with the selective agonist Lys-des-Arg9-BK failed to reproduce BK actions on ENaC. This is consistent with B2 receptors playing a critical role in mediating BK signaling to ENaC. BK has little effect on ENaC Po when Gq/11 was inhibited with Gp antagonist 2A. Moreover, inhibition of phospholipase C (PLC) with U73122, but not saturation of cellular cAMP levels with the membrane-permeable nonhydrolysable cAMP analog 8-cpt-cAMP, prevents BK actions on ENaC activity. This argues that BK stimulates B2 receptors with subsequent activation of Gq/11-PLC signaling cascade to acutely inhibit ENaC activity. Activation of BK signaling acutely depletes apical PI( 4 , 5 )P2 levels. However, inhibition of Ca2+ pump SERCA of the endoplasmic reticulum with thapsigargin does not prevent BK signaling to ENaC. Furthermore, caffeine, while producing a similar rise in [Ca2+]i as in response to BK stimulation, fails to recapitulate BK actions on ENaC. Therefore, we concluded that BK acutely inhibits ENaC Po in mammalian ASDN via stimulation of B2 receptors and following depletion of PI( 4 , 5 )P2, but not increases in [Ca2+]i.

Download Full-text

Effects of thyroid hormones on urinary and renal kallikreins

AJP Endocrinology and Metabolism ◽

10.1152/ajpendo.1992.263.3.e430 ◽

1992 ◽

Vol 263 (3) ◽

pp. E430-E434

Author(s):

S. Avigdor ◽

F. Alhenc-Gelas ◽

J. Bouhnik

Keyword(s):

Thyroid Hormones ◽

Urinary Excretion ◽

Plasma Aldosterone ◽

Urinary Kallikrein ◽

Single Measurement ◽

Kidney Weight ◽

Plasma Aldosterone Concentration ◽

Renal Kallikrein ◽

Enzyme Changes ◽

Intact Rats

The effects of thyroid hormones on the urinary excretion of kallikrein and on renal kallikrein were studied in rats. Total and active urinary kallikrein was decreased after thyroidectomy, but renal kallikrein content remained unchanged. Diuresis increased, and kidney weight and plasma aldosterone concentration decreased. Treatment with 3,5,3'-triiodo-L-thyronine restored the urinary kallikrein in thyroidectomized rats to normal and increased it in intact rats. It also produced increases in kidney weight and plasma aldosterone and a decrease in diuresis. The effect of thyroid hormones on the urinary kallikrein response to mineralocorticoids was also tested. Deoxycorticosterone acetate increased urinary kallikrein more in normal than in thyroidectomized rats. These results suggest that thyroidectomy decreases renal kallikrein synthesis and lowers the turnover rate of the enzyme, changes not detectable by a single measurement of the renal kallikrein content but reflected by an alteration in the urinary excretion of the enzyme. Thyroid hormones participate in the control of urinary kallikrein. This effect, however, is probably indirect and may be mediated by mineralocorticoids since thyroid function affects both the plasma level of aldosterone, which is known to influence renal kallikrein, and the kallikrein response to exogenous mineralocorticoids.

Download Full-text

Hypokalemia induces renal injury and alterations in vasoactive mediators that favor salt sensitivity

AJP Renal Physiology ◽

10.1152/ajprenal.2001.281.4.f620 ◽

2001 ◽

Vol 281 (4) ◽

pp. F620-F629 ◽

Cited By ~ 69

Author(s):

Shin-Ichi Suga ◽

M. Ian Phillips ◽

Patricio E. Ray ◽

James A. Raleigh ◽

Carlos P. Vio ◽

...

Keyword(s):

Renal Injury ◽

Renin Angiotensin System ◽

Salt Sensitivity ◽

Prostaglandin E ◽

Tubulointerstitial Injury ◽

Angiotensin System ◽

Vasoactive Mediators ◽

Hypoxia Marker ◽

Renal Kallikrein ◽

Salt Sensitive Hypertension

We investigated the hypothesis that hypokalemia might induce renal injury via a mechanism that involves subtle renal injury and alterations in local vasoactive mediators that would favor sodium retention. To test this hypothesis, we conducted studies in rats with diet-induced K+deficiency. We also determined whether rats with hypokalemic nephropathy show salt sensitivity. Twelve weeks of hypokalemia resulted in a decrease in creatinine clearance, tubulointerstitial injury with macrophage infiltration, interstitial collagen type III deposition, and an increase in osteopontin expression (a tubular marker of injury). The renal injury was greatest in the outer medulla with radiation into the cortex, suggestive of an ischemic etiology. Consistent with this hypothesis, we found an increased uptake of a hypoxia marker, pimonidazole, in the cortex. The intrarenal injury was associated with increased cortical angiontensin-converting enzyme (ACE) expression and continued cortical angiotensin II generation despite systemic suppression of the renin-angiotensin system, an increase in renal endothelin-1, a decrease in renal kallikrein, and a decrease in urinary nitrite/nitrates and prostaglandin E2 excretion. At 12 wk, hypokalemic rats were placed on a normal-K+ diet with either high (4%)- or low (0.01%)-NaCl content. Despite correction of hypokalemia and normalization of renal function, previously hypokalemic rats showed an elevated blood pressure in response to a high-salt diet compared with normokalemic controls. Hypokalemia is associated with alterations in vasoactive mediators that favor intrarenal vasoconstriction and an ischemic pattern of renal injury. These alterations may predispose the animals to salt-sensitive hypertension that manifests despite normalization of the serum K+.

Download Full-text