Low salt diet downregulates plasma but not tissue kallikrein-kinin
system.
U., Hilgenfeldt, T. Puschner, U. Riester, J. Finsterle, J.
Hilgenfeldt, and E. Ritz.
Department of Pharmaceutical Pharmacology, and Department of
Nephrology, University of Heidelberg and Central Laboratory of BfA,
Bad Kissingen, Germany
APStracts 5:0071F, 1998.
The kallikrein-kinin system (KKS) is involved in the regulation of
blood pressure and in the sodium and water excretion. In humans the
KKS is divided functionally into a plasma KKS generating the
biologically active peptide bradykinin and into the tissue
(glandular) KKS generating the active peptide kallidin. The objective
of this study was to examine the effect of a low-NaCl diet on the
concentration of both plasma- and tissue-KKS in plasma and urine in
ten healthy volunteers. After a 4-day low-NaCl diet the urinary
sodium and chloride excretion had decreased from 234 to 21.2 mmol/24h
and from 198 to 14.6 mmol/24h, respectively. The AngI-, aldosterone-,
and ACE-plasma levels significantly increased from 50.4 to 82.8 pg
ml-1, from 129 to 315 pg ml-1, and from 46,4 to 59,8 U ml-1,
respectively, demonstrating the physiological adjustment to the low
salt diet. In plasma the levels of bradykinin and plasma kallikrein
had significantly decreased from 13.7 to 7.57 pg ml-1 and 14.4 to
7.13 U ml-1, respectively. However the levels of high-molecular
-weight kininogen (HMW-kininogen) remain unchanged ( 101 vs. 112 [mu]g
ml-1, NS). Contrary to plasma kallikrein the plasma levels of tissue
kallikrein increased (0.345 vs. 0.500 U ml-1; P<0,01). The plasma
kallidin levels, however, did not change (64,7 vs. 68,6pg ml-1, NS).
This can be explained by a simultaneous decrease in the plasma low
-molecular-weight kininogen (LMW-kininogen) levels (89,9 vs. 44,4
[mu]g ml-1; P<0,05). As in plasma we find increased urinary
concentrations of renal (tissue) kallikrein (23,3 to 42,8 U/24h;
P<0,05) that contrast with, and are presumably counterbalanced by
urinary LMW-kininogen levels (77,0 vs. 51,8 [mu]g/24h; P<0,05).
Consequently in urine low NaCl diet caused no significant change in
either bradykinin or kallidin (9,2 vs. 10,8 [mu]g/24h, and 10,9 vs.
10,3 [mu]g/24h). It is concluded that the stimulation of the renin
-angiotensin system on a low NaCl diet is associated with a decrease
in plasma KKS (bradykinin and plasma kallikrein), but not in tissue
and renal KKS. Although tissue kallikrein is increased there is no
change in kallidin, as LMW-kininogen in plasma and urine is
decreased. These data suggest a difference in the regulation of
plasma- and tissue KKS by low salt diet.
Received 18 September 1997; accepted in final form 9 March 1998.
APS Manuscript Number F302-7.
Article publication pending Am. J. Physiol. (Renal Physiology).
ISSN 1080-4757 Copyright 1998 The American Physiological Society.
Published in APStracts on 6 April 1998