Coordinate changes of renin and brain-type nitric-oxide-synthase (b-NOS) mRNA levels in rat kidneys.
In our study we have examined the mRNA levels of nitric-oxide-(NO-)synthases in rat kidneys during states of stimulated and reduced renin gene expression, to find out whether renal mRNA levels of NO-synthases are correlated with the activity of the renin system. Stimulation of the renin system was achieved by unilateral renal artery clipping (2-kidney/1-clip rats), treatment with the angiotensin II (ANG II) antagonist losartan (40 mg/kg), application of furosemide (12 mg x kg-1 x day-1) and a low-sodium diet (0.02% w/w Na+), which increased renin mRNA levels to 464%, 495%, 309% and 219% of those of control animals, respectively. Inhibition of the renin system was achieved in the nonclipped (contralateral) kidneys of 2-kidney/1-clip rats and in the kidneys of rats which were fed a high-sodium diet (4% w/w Na+); in both cases renin mRNA levels decreased to about 50% of the control values. First screening of the gene expression of brain-type NO-synthase (b-NOS), endothelial NOS (e-NOS) and inducible NOS (i-NOS) during all these alterations of the renin system was done using the reverse transcriptase-polymerase chain reaction (RT-PCR) technique. Results from such noncompetitive PCR experiments indicated that only b-NOS mRNA levels change concordantly with the levels of renin. These changes in b-NOS mRNA levels were checked by the more reliable method of RNase protection assay. Results of the RNase protection assay proved that the renal levels of b-NOS mRNA were significantly increased by about 50% after a low-sodium diet and hypoperfusion of the kidney. Given a stimulatory role of endothelium-derived relaxing factor (EDRF)/NO on the renin system our findings may provide the first evidence that increases of renal levels of b-NOS mRNA and, as a consequence, of renal EDRF/NO formation could be important mediators of the well-known effect of salt intake and hypoperfusion on the renin system.
Schricker
K
K
Institut für Physiology I, Universität Regensburg, Postfach 101042, D-93040 Regensburg, Germany.
Pötzl
B
B
Hamann
M
M
Kurtz
A
A
D000804:Angiotensin II / Q000378:metabolism; D057911:Angiotensin Receptor Antagonists; D000818:Animals; D009320:Atrial Natriuretic Factor / Q000096:biosynthesis; D001483:Base Sequence; D001921:Brain / Q000201:enzymology*; D006978:Hypertension, Renovascular / Q000201:enzymology; D007668:Kidney / Q000187:drug effects / Q000201:enzymology*; D008297:Male; D008969:Molecular Sequence Data; D019001:Nitric Oxide Synthase / Q000096:biosynthesis*; D016133:Polymerase Chain Reaction; D012333:RNA, Messenger / Q000096:biosynthesis*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012077:Renal Artery / Q000502:physiology; D012083:Renin / Q000378:metabolism*
D057911:Angiotensin Receptor Antagonists; D012333:RNA, Messenger; D000804:Angiotensin II; D009320:Atrial Natriuretic Factor; D019001:Nitric Oxide Synthase; D012083:Renin