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Atrial natriuretic factor selectively increases renal blood flow in conscious spontaneously hypertensive rats
European Journal of Pharmacology, 104 (1984) 391-392
391
Elsevier
Rapid communication A T R I A L N A T R I U R E T I C F A C T O R S E L E C T I V E L Y I N C R E A S E S R E N A L B L O O D F L O W IN CONSCIOUS SPONTANEOUSLY HYPERTENSIVE RATS HIROYUKI KOIKE *, TOSHIO SADA, MASAAKI MIYAMOTO, KIYOSHI OIZUMI, MITSUO SUGIYAMA and TADASHI INAGAMI ** Biological and Chemical L~zboratories. Sankyo Co. LTD.. 1-2-58 ftiromachi. Shinagawa-ku, Biochemistry, School of Medicine, Vanderhilt Unit,ersiO', Nasht,ille, TN 37232. U.S.A.
Tokyo, Japan and ** Department o/
Received 13 August 1984, accepted 13 August 1984
T h e atria of the heart have long been k n o w n to p a r t i c i p a t e in the reflex control of fluid volume; physiological s t i m u l a t i o n of atrial receptors elicits water diuresis a n d h y p o t e n s i o n . This reflex h y p o tension is c h a r a c t e r i z e d b y a selective increase of renal b l o o d flow due to w i t h d r a w a l of s y m p a t h e t i c o u t f l o w to the k i d n e y (for review see Bishop et al., 1983). On the o t h e r hand, the atria have been shown to c o n t a i n a g r o u p of p e p t i d e s called atrial n a t r i u r e t i c factor ( A N F , for review see Sagnella a n d M a c G r e g o r , 1984). These p e p t i d e s have, in a d d i t i o n to their p o w e r f u l n a t r i u r e t i c action, a vascular r e l a x a n t action. The p h y s i o l o g i c a l role of the p e p t i d e s is not clear at present though circ u m s t a n t i a l evidence suggests that they are released in the b l o o d s t r e a m when b l o o d v o l u m e is e x p a n d e d a n d that they serve as circulating h o r m o n e s c o n t r o l l i n g b l o o d volume. By a n a l o g y with fluid v o l u m e regulation b y reflexes arising in the atria, we h y p o t h e s i z e d that A N F causes a selective increase of renal b l o o d flow when injected intravenously. To test this hyp o t h e s i s we studied the h e m o d y n a m i c effects of A N F using the tracer m i c r o s p h e r e technique. W e used an A N F of 25 a m i n o - a c i d s synthesized in our l a b o r a t o r i e s . The chemical characteristics and biological activities of the synthetic A N F have p r o v e n identical to those of the n a t u r a l A N F which was e x t r a c t e d from rat a t r i u m a n d sequenced by M i s o n o et al. (1984). M a l e s p o n t a n e o u s l y h y p e r t e n s i v e rats ( S H R ) weighing 320-400 g were c a n n u l a t e d u n d e r * To whom all correspondence should be addressed. 0014-2999/84/$03.00 :c 1984 Elsevier Science Publishers B.V.
anesthesia with p e n t o b a r b i t a l . O n e c a n n u l a was p l a c e d in the femoral artery for m o n i t o r i n g b l o o d pressure a n d d r a w i n g a reference b l o o d s a m p l e a n d the other was p l a c e d in the left ventricle for injecting microspheres. On the d a y following surgery the a n i m a l s were d i v i d e d into 2 g r o u p s a n d used in the conscious state for a h e m o d y n a m i c study. The A N F group received 30 b t g / k g i.v. of A N F and the control group 0.5 m l / k g i.v. of saline. M i c r o s p h e r e s (15 + 3 /~m in d i a m e t e r ) labelled with a41Ce were injected 5 min after adm i n i s t r a t i o n of either A N F or saline, while a reference b l o o d s a m p l e was c o n t i n u o u s l y d r a w n over a p e r i o d of 1.5 min. The animal was sacrificed a n d its organ excised for the m e a s u r e m e n t of o r g a n weight and radioactivity. A N F p r o d u c e d long-lasting h y p o t e n s i o n with a d u r a t i o n of m o r e than 30 min. T a b l e 1 s u m m a r i z e s systemic a n d regional h e m o d y n a m i c s m e a s u r e d 5 min after a d m i n i s t r a t i o n of the agent. A t this time the b l o o d pressure of the A N F group reached a nadir, and heart rate a n d c a r d i a c o u t p u t t e n d e d to increase. Blood flow in the k i d n e y was signific a n t l y increased in the A N F group as c o m p a r e d with the control group, whereas b l o o d flows in o t h e r organs r e m a i n e d unchanged. These d a t a indicate that A N F selectively increased renal b l o o d flow in conscious S H R . Blood flow in organs o t h e r than the k i d n e y d i d not decrease in the face of d e c r e a s e d b l o o d pressure, suggesting that vasodilat a t i o n occurred in the whole body. Indeed, the c a l c u l a t e d total p e r i p h e r a l resistance decreased slightly in the A N F group. The b l o o d pressure lowering effect of atrial
392 TABLE l
p r e s e n t s t u d y , at l e a s t t h e a c u t e h y p o t e n s i v e e f f e c t
Systemic and regional hemodynamics following intravenous injection of saline (control) or ANF ~
o f A N F a p p e a r e d to r e s u l t f r o m v a s o d i l a t a t i o n in
Control Initial MBP 153 ± 2 (mmHg) Initial HR 326 + 9 (beats/min) MBP 150 + 3 (mmHg) HR 325 + 10 (beats/rain) CO 280 + 6 (ml/min per kg) TPR 0.54+ 0 . 0 1 (mmHg/ml per min per kg) Regional blood flows (ml / min per 100 g) Brain 119 + 8 Heart 475 + 33 Spleen 140 _+16 Kidney 486 + 46 Small intestine 230 + 16 Skeletalmuscle 13 _+ 2 Testis 33 + I
ANF 156
t h e w h o l e b o d y , e s p e c i a l l y in t h e k i d n e y . In a g r e e m e n t w i t h t h e p r e s e n t r e s u l t s , O s h i m a et al. (1984),
± 4
338
± 8
141
± 3b
u s i n g b l o o d - p e r f u s e d p r e p a r a t i o n s o f t h e rat, h a v e s h o w n t h a t rat a t r i a l e x t r a c t s p r o d u c e d
a more
p o w e r f u l v a s o d i l a t a t i o n in the r e n a l v a s c u l a r b e d t h a n in t h e h i n d q u a r t e r s .
348
± 13
303
± 21
It is u n l i k e l y t h a t A N F
is i n v o l v e d in fluid
v o l u m e r e g u l a t i o n b y r e f l e x e s a r i s i n g in t h e atria. T h e selective renal vasodilatation however seems t o b e c o m m o n to h u m o r a l a n d n e u r a l m e c h a n i s m s o f fluid v o l u m e r e g u l a t i o n o r i g i n a t i n g in t h e atria.
0.48± 0.03
125 530 142 664 218 15 35
+ 8 ± 53 + 15 + 69 b ± 20 ± 1 ± 2
MBP: mean blood pressure: HR: heart rate: CO: cardiac output: TPR: total peripheral resistance. All values are expressed as means+S.E. (n=8). b p < 0 . 0 5 by nonpaired t-test between control and ANF. a
e x t r a c t s h a s b e e n d e m o n s t r a t e d b y D e B o l d et al. (1981). T h e y a t t r i b u t e d t h e h y p o t e n s i o n to loss o f b o d y fluid b e c a u s e the h e m a t o c r i t i n c r e a s e d after i n t r a v e n o u s i n j e c t i o n o f t h e e x t r a c t in t h e i r e x p e r i ment. However, j u d g i n g from the results of the
References
Bishop, V.A., A. Mall±an± and P. ThOren, 1983, Cardiac mocha noreceptors, in: Handbook of Physiology, Section 2. The Cardiovascular System, Vol. III, eds. J.T. Shepherd and F.M. Abboud (American Physiological Society, Bethesda) p. 497. De Bold, A.J., H.B. Bornstein, A.T. Veress and H. Sonnenberg, 1981, A rapid and potent natriuretic response to intravenous injection of atrial myocardial extract in rats, Life Sci. 28, 89. Misono, K.S., H. Fukumi, R.T. (;rammer and T. lnagami, 1984, Rat atrial natriuretic factor: Complete amino acid sequence and disulfide linkage essential for biological activ ity, Biochem. Biophys. Res. Commun. 119, 524. Oshima, T., M.G. Currie, D.M. Geller and P. Ncedleman, 1984, An atrial peptide is a potent renal vasodilator sub stance, Circ. Res. 54, 612. Sagnella, G.A. and G.A. MacGregor, 1984, Cardiac peptides and control of sodium excretion, Nature 309, 666.
391
Elsevier
Rapid communication A T R I A L N A T R I U R E T I C F A C T O R S E L E C T I V E L Y I N C R E A S E S R E N A L B L O O D F L O W IN CONSCIOUS SPONTANEOUSLY HYPERTENSIVE RATS HIROYUKI KOIKE *, TOSHIO SADA, MASAAKI MIYAMOTO, KIYOSHI OIZUMI, MITSUO SUGIYAMA and TADASHI INAGAMI ** Biological and Chemical L~zboratories. Sankyo Co. LTD.. 1-2-58 ftiromachi. Shinagawa-ku, Biochemistry, School of Medicine, Vanderhilt Unit,ersiO', Nasht,ille, TN 37232. U.S.A.
Tokyo, Japan and ** Department o/
Received 13 August 1984, accepted 13 August 1984
T h e atria of the heart have long been k n o w n to p a r t i c i p a t e in the reflex control of fluid volume; physiological s t i m u l a t i o n of atrial receptors elicits water diuresis a n d h y p o t e n s i o n . This reflex h y p o tension is c h a r a c t e r i z e d b y a selective increase of renal b l o o d flow due to w i t h d r a w a l of s y m p a t h e t i c o u t f l o w to the k i d n e y (for review see Bishop et al., 1983). On the o t h e r hand, the atria have been shown to c o n t a i n a g r o u p of p e p t i d e s called atrial n a t r i u r e t i c factor ( A N F , for review see Sagnella a n d M a c G r e g o r , 1984). These p e p t i d e s have, in a d d i t i o n to their p o w e r f u l n a t r i u r e t i c action, a vascular r e l a x a n t action. The p h y s i o l o g i c a l role of the p e p t i d e s is not clear at present though circ u m s t a n t i a l evidence suggests that they are released in the b l o o d s t r e a m when b l o o d v o l u m e is e x p a n d e d a n d that they serve as circulating h o r m o n e s c o n t r o l l i n g b l o o d volume. By a n a l o g y with fluid v o l u m e regulation b y reflexes arising in the atria, we h y p o t h e s i z e d that A N F causes a selective increase of renal b l o o d flow when injected intravenously. To test this hyp o t h e s i s we studied the h e m o d y n a m i c effects of A N F using the tracer m i c r o s p h e r e technique. W e used an A N F of 25 a m i n o - a c i d s synthesized in our l a b o r a t o r i e s . The chemical characteristics and biological activities of the synthetic A N F have p r o v e n identical to those of the n a t u r a l A N F which was e x t r a c t e d from rat a t r i u m a n d sequenced by M i s o n o et al. (1984). M a l e s p o n t a n e o u s l y h y p e r t e n s i v e rats ( S H R ) weighing 320-400 g were c a n n u l a t e d u n d e r * To whom all correspondence should be addressed. 0014-2999/84/$03.00 :c 1984 Elsevier Science Publishers B.V.
anesthesia with p e n t o b a r b i t a l . O n e c a n n u l a was p l a c e d in the femoral artery for m o n i t o r i n g b l o o d pressure a n d d r a w i n g a reference b l o o d s a m p l e a n d the other was p l a c e d in the left ventricle for injecting microspheres. On the d a y following surgery the a n i m a l s were d i v i d e d into 2 g r o u p s a n d used in the conscious state for a h e m o d y n a m i c study. The A N F group received 30 b t g / k g i.v. of A N F and the control group 0.5 m l / k g i.v. of saline. M i c r o s p h e r e s (15 + 3 /~m in d i a m e t e r ) labelled with a41Ce were injected 5 min after adm i n i s t r a t i o n of either A N F or saline, while a reference b l o o d s a m p l e was c o n t i n u o u s l y d r a w n over a p e r i o d of 1.5 min. The animal was sacrificed a n d its organ excised for the m e a s u r e m e n t of o r g a n weight and radioactivity. A N F p r o d u c e d long-lasting h y p o t e n s i o n with a d u r a t i o n of m o r e than 30 min. T a b l e 1 s u m m a r i z e s systemic a n d regional h e m o d y n a m i c s m e a s u r e d 5 min after a d m i n i s t r a t i o n of the agent. A t this time the b l o o d pressure of the A N F group reached a nadir, and heart rate a n d c a r d i a c o u t p u t t e n d e d to increase. Blood flow in the k i d n e y was signific a n t l y increased in the A N F group as c o m p a r e d with the control group, whereas b l o o d flows in o t h e r organs r e m a i n e d unchanged. These d a t a indicate that A N F selectively increased renal b l o o d flow in conscious S H R . Blood flow in organs o t h e r than the k i d n e y d i d not decrease in the face of d e c r e a s e d b l o o d pressure, suggesting that vasodilat a t i o n occurred in the whole body. Indeed, the c a l c u l a t e d total p e r i p h e r a l resistance decreased slightly in the A N F group. The b l o o d pressure lowering effect of atrial
392 TABLE l
p r e s e n t s t u d y , at l e a s t t h e a c u t e h y p o t e n s i v e e f f e c t
Systemic and regional hemodynamics following intravenous injection of saline (control) or ANF ~
o f A N F a p p e a r e d to r e s u l t f r o m v a s o d i l a t a t i o n in
Control Initial MBP 153 ± 2 (mmHg) Initial HR 326 + 9 (beats/min) MBP 150 + 3 (mmHg) HR 325 + 10 (beats/rain) CO 280 + 6 (ml/min per kg) TPR 0.54+ 0 . 0 1 (mmHg/ml per min per kg) Regional blood flows (ml / min per 100 g) Brain 119 + 8 Heart 475 + 33 Spleen 140 _+16 Kidney 486 + 46 Small intestine 230 + 16 Skeletalmuscle 13 _+ 2 Testis 33 + I
ANF 156
t h e w h o l e b o d y , e s p e c i a l l y in t h e k i d n e y . In a g r e e m e n t w i t h t h e p r e s e n t r e s u l t s , O s h i m a et al. (1984),
± 4
338
± 8
141
± 3b
u s i n g b l o o d - p e r f u s e d p r e p a r a t i o n s o f t h e rat, h a v e s h o w n t h a t rat a t r i a l e x t r a c t s p r o d u c e d
a more
p o w e r f u l v a s o d i l a t a t i o n in the r e n a l v a s c u l a r b e d t h a n in t h e h i n d q u a r t e r s .
348
± 13
303
± 21
It is u n l i k e l y t h a t A N F
is i n v o l v e d in fluid
v o l u m e r e g u l a t i o n b y r e f l e x e s a r i s i n g in t h e atria. T h e selective renal vasodilatation however seems t o b e c o m m o n to h u m o r a l a n d n e u r a l m e c h a n i s m s o f fluid v o l u m e r e g u l a t i o n o r i g i n a t i n g in t h e atria.
0.48± 0.03
125 530 142 664 218 15 35
+ 8 ± 53 + 15 + 69 b ± 20 ± 1 ± 2
MBP: mean blood pressure: HR: heart rate: CO: cardiac output: TPR: total peripheral resistance. All values are expressed as means+S.E. (n=8). b p < 0 . 0 5 by nonpaired t-test between control and ANF. a
e x t r a c t s h a s b e e n d e m o n s t r a t e d b y D e B o l d et al. (1981). T h e y a t t r i b u t e d t h e h y p o t e n s i o n to loss o f b o d y fluid b e c a u s e the h e m a t o c r i t i n c r e a s e d after i n t r a v e n o u s i n j e c t i o n o f t h e e x t r a c t in t h e i r e x p e r i ment. However, j u d g i n g from the results of the
References
Bishop, V.A., A. Mall±an± and P. ThOren, 1983, Cardiac mocha noreceptors, in: Handbook of Physiology, Section 2. The Cardiovascular System, Vol. III, eds. J.T. Shepherd and F.M. Abboud (American Physiological Society, Bethesda) p. 497. De Bold, A.J., H.B. Bornstein, A.T. Veress and H. Sonnenberg, 1981, A rapid and potent natriuretic response to intravenous injection of atrial myocardial extract in rats, Life Sci. 28, 89. Misono, K.S., H. Fukumi, R.T. (;rammer and T. lnagami, 1984, Rat atrial natriuretic factor: Complete amino acid sequence and disulfide linkage essential for biological activ ity, Biochem. Biophys. Res. Commun. 119, 524. Oshima, T., M.G. Currie, D.M. Geller and P. Ncedleman, 1984, An atrial peptide is a potent renal vasodilator sub stance, Circ. Res. 54, 612. Sagnella, G.A. and G.A. MacGregor, 1984, Cardiac peptides and control of sodium excretion, Nature 309, 666.