194 Blood A in t h e 1st (p > 0.05). was 1.65 • series).

Specialia levels a t t a i n e d d u r i n g t h e h o r m o n e i n f u s i o n a n d 2rid series d i d n o t differ s i g n i f i c a n t l y T h e c o n c e n t r a t i o n of A a t t h e e n d of i n f u s i o n 0.28 tzg/1 (1st series) a n d 1.56 • 0.29 ~,g/l (2nd

Discussion. T h e r e s u l t s o b t a i n e d show t h a t t h e h y p e r glycemic effect of A is m u c h smaller in t h e dogs p r e v i o u s l y exercizing u n t i l e x h a u s t i o n t h a n in t h e s a m e dogs infused a t rest w i t h o u t p r e c e d i n g p h y s i c a l effort. T h i s p h e n o m e n o n c a n n o t be a t t r i b u t e d to t h e i n c r e a s e d u p t a k e of glucose b y t h e muscles d e p l e t e d of glycogen, since t h e r e was no s i g n i f i c a n t increase in t h e muscle glycogen c o n t e n t following A infusion. T h e w e a k e r effect of a d r e n a l i n e a f t e r exercise m a y b e c a u s e d b y a n e x h a u s t i o n of t h e liver glycogen, insufficient gluconeogenesis, or b y a decreased r e a c t i v i t y of t h e liver e n z y m a t i c s y s t e m s t o a d r e n a l i n e . A decrease of t h e liver glycogen c o n t e n t a f t e r e x h a u s t i n g p h y s i c a l w o r k h a s b e e n f o u n d in h u m a n s u b j e c t s ; h o w e v e r some a m o u n t of t h e liver glycogen seemed t o be n o t a v a i l a b l e for glycogenolytic f a c t o r s a c t i n g d u r i n g exercise s. I n t h e p r e s e n t i n v e s t i g a t i o n , F F A r e s p o n s e to A

8 t~. HULTMAN, in Frontiers oJ Fitness (Ed. R. J. SHEPARD; Ch. Thomas Publ., Springfield 1972). 9 ~u C. RIDDLE, W. G. RYAN and T. B. SCttWARTZ,Metabolism 27, 1063 (1972). 10 The authors thank Mrs. 12. KOSSOWSKA, W. RADZISZEWSKA,and Mr. R. SZOSTAKfor their valuable technicaI assistance.

Catecholamines

t~XPERIENTIA 31/2

in tile dogs infused u n d e r r e s t i n g c o n d i t i o n s d i d n o t differ s i g n i f i c a n t l y f r o m t h a t f o u n d a f t e r e x h a u s t i n g exercise. On t h e c o n t r a r y , a n i n c r e a s e d adipose tissue r e s p o n s i v e n e s s to N A a f t e r p r e c e d i n g p h y s i c a l a c t i v i t y was described in h u m a n s 9. A d r e n a l i n e - i n d u c e d increase of L A a f t e r exercise in s p i t e of glycogen d e p l e t i o n f r o m t h e w o r k i n g muscles suggests t h a t it o r i g i n a t e d f r o m n o n - w o r k i n g muscles. S u m m a r i z i n g , tile d a t a o b t a i n e d in t h e p r e s e n t s t u d y d e m o n s t r a t e t h a t t h e h y p e r g l y c e m i c effect of A is m a r k e d l y r e d u c e d a f t e r p r o l o n g e d exercise. H o w e v e r , it is still possible to increase b l o o d glucose c o n c e n t r a t i o n b y a d r e n a l i n e in t h i s s i t u a t i o n . T h u s , a decrease in b l o o d A level m a y be p a r t l y r e s p o n s i b l e for t h e h y p o g l y c e m i a f o u n d a t t h e e n d of p r o l o n g e d e x h a u s t i n g exercise in dogs.

Rdsumd. Les c h a n g e m e n t s de c o n c e n t r a t i o n de glucose, F F A et L A r 6 s u l t a n t d ' u n e i n f u s i o n i n t r a v 6 n a l e d ' a d r 6 n a line o n t 6t6 6tndi6s chez des chiens a y a n t 6t6 soumis u n exercice p h y s i q u e prolong6. On a c o n s t a t 6 u n abaissemerit de l'effet h y p e r g l y c 6 m i q u e de l ' a d r 6 n a l i n e . Les autres param3tres changeaient semblablement, comme d a n s les c o n d i t i o n s de contr61e, sans effort p h y s i q u e pr6alable. A. W. ZIEMBA, S, KOZLOWSKI, K. NAZAR, Z. BRZEZI~SKA a n d H. I'~ACIUBA-UgcILKO 10 Laboratory o/A ppHed Physiology, Medical Research Centre, Polish Academy o/Sciences Jazgarzewska I, P-00-730 Warszawa (Poland), 28 August 7974.

in Fetal and Neonatal Rabbit Heart

I t is well k n o w n t h a t i m p o r t a n t physiological c h a n g e s occur a t b i r t h 1. T h e f e t a l suffering c o n d i t i o n s w h i c h exist a t p a r t u r i t i o n , a n d t h e s u d d e n a d a p t a t i o n of t h e new'b o r n to a t m o s p h e r i c life, are p r o b a b l y a c c o m p a n i e d b y m o d i f i c a t i o n s of n e u r o - e n d o c r i n e s y s t e m a c t i v i t y . T h e a d r e n a l c a t e c h o l a m i n e s store h a s b e e n f o u n d t o decline i m m e d i a t e l y a f t e r b i r t h , in r a t s 2 a n d r a b b i t s 2, a, w h i l e in r a b b i t s t h e level of p l a s m a n o r e p i n e p h r i n e increased a t p a r t u r i t i o n ~. T h i s s t u d y was u n d e r t a k e n to d e t e r m i n e w h e t h e r or n o t t h e c a r d i a c c a t e c h o l a m i n e store c h a n g e s in t h e f e t u s n e a r t e r m a n d w i t h i n t h e first few h o u r s a f t e r parturition. Materials and methods. T h e e x p e r i m e n t s were carried o u t o n fetuses a n d n e w - b o r n r a b b i t s of t h e w h i t e N e w Z e a l a n d strain. I n t h e l a s t 2 d a y s of p r e g n a n c y ( t e r m = 31 days), t h e female r a b b i t s were killed b y air e m b o l i s m , l a p a r o t o m y was p e r f o r m e d a n d t h e fetuses were t a k e n o u t i m m e d i a t e l y a n d d e c a p i t a t e d . T h e h e a r t s were q u i c k l y r e m o v e d , w a s h e d w i t h ice-cold 0.9% NaC1, b l o t t e d o n filter p a p e r a n d frozen a t once. I t was n e c e s s a r y t o pool 4 t o 5 of t h e h e a r t s f r o m f e t a l a n i m a l s (from t h e s a m e litter) t o p r o v i d e sufficient tissue for one single n o r e p i n e p h r i n e and epinephrine determination. The new-born rabbits were d e c a p i t a t e d e i t h e r j u s t a t b i r t h or l a t e r on, a n d t h e s a m p l e s were p r e p a r e d as w i t h t h e fetuses. T h e tissue was h o m o g e n i z e d in ice-cold 0.4 M p e r c h l o r i c acid b y u s i n g a Tri-Rtissue homogenizer (Genelab International) provided w i t h a glass pestle. H o m o g e n a t e s were k e p t on ice u n t i l c e n t r i f u g e d a t 9,000 • a t 0~ for 30 min. T h e residues were r e - e x t r a c t e d t w i c e m o r e a n d all 3 s u p e r n a t a n t s were pooled 5. T h e p H was a d j u s t e d t o 8.5 w i t h 0.5 M Tris b u f f e r 6 a n d t h e s a m p l e s were a d s o r b e d o n t o a l u m i n a 7 (Merck A l u m i n i u m o x i d e active, acidic a c t i v i t y I), p r e p a r e d b y t h e m e t h o d of ANTON a n d SAYRE s. T h e

a l u m i n a c o n t a i n i n g t h e a d s o r b e d c a t e c h o l a m i n e s was w a s h e d w i t h hi-distilled water. A f t e r c e n t r i f u g a t i o n , t h e s u p e r n a t a n t was carefully a s p i r a t e d off. E l u t i o n was p e r f o r m e d w i t h 3 • 2 m l of 0.3 N acetic acid w h i c h was thoroughly mixed with the alumina by using a magnetic stirrer. All 3 e l u a t e s were pooled, c e n t r i f u g e d , a d j u s t e d t o p H 6.5 a n d used for f l u o r o m e t r i c a s s a y 9. F o r fluorom e t r i c m e a s u r e m e n t , a n A m i n c o - B o w m a n Spectrof l u o r i m e t e r w i t h ellipsoidal m i r r o r was used. R e a d i n g s were m a d e a t a c t i v a t i o n w a v e l e n g t h s of 380 a n d 430 n m a n d a t fluorescence w a v e l e n g t h s of 490 a n d 540 n m . T h e m e a n v a l u e s :k S E M are g i v e n in n g / g a n d n g / s i n g l e h e a r t . T h e t-test was c o m p u t e d . Results. I n t h e 30- a n d 31-day-old f e t a l r a b b i t h e a r t ( g e s t a t i o n a l age), t h e n o r e p i n e p h r i n e level is low. As no c h a n g e was o b s e r v e d f r o m one d a y to a n o t h e r , we h a v e pooled t h e values. T h e i r m e a n v a l u e is 85 • 12 rig/g, as c a n

1 C-. S. DAWES, in Foetal and Neonatal Physiology (Year Book Medical Publ., Chicago 1969), p. 117. 2 j. ROFFI, J. L. FROGER and M. F. DEBRAY. C. r. Acad. Sci., Paris 287, 595 (1973). 3 j. ROFFI, J. Physiol., Paris 56, 434 (1964). 4 K. OKYAYUZand R. GHAMBIR, Experientia 29, 1472 (1973). 5 A. BERTLER, A. CARLSSON and E. ROSI~GREN, Acta physiol. scand. 4/4, 273 (1958). 6 j. p. HANIG, J. Iv[. ~V[ORRISONand S. IKRoPs, Anatyt. chim. Acta

59, 363 (1972). T V. RENZINI, C. A. BRUNORIand C. VAI.ORI, Clin. chim. Acta 30, 587 (1970). 8 A. H. ANTON and D. F. SAYRE, J. Pharmac. exp. Ther. 138, 360 (1962). 9 U. S. VON EULER and Iv. LISHAJKO, Acta physiol, scand. 57, 348 (1961).

15.2. 1975

be seen in F i g u r e 1. A b o u t t h e s a m e level was f o u n d a t p a r t u r i t i o n . T h e n , s u d d e n l y , w i t h i n 1 t o 4 h, t h e level of n o r e p i n e p h r i n e increases to 145 • 16 n g / g (p < 0.005). A t a m o r e a d v a n c e d age (33-72 h), t h e m e a n v a l u e r e a c h e s 154 • 18 ng/g. A s i m i l a r e v o l u t i o n c a n b e seen w h e n t h e v a l u e s are e x p r e s s e d in n g / s i n g l e h e a r t . T h e e p i n e p h r i n e level is v e r y low as c o m p a r e d to nore p i n e p h r i n e : 5 t o 6-fold less in t h e f e t u s a n d a t p a r t u r i t i o n , d o w n to 14-fold a t a m o r e a d v a n c e d age (see F i g u r e 2). I n t h e f e t a l period, t h e m e a n v a l u e is 17 • 4 n g / g a n d

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Fig. 1. Norepinephrine level in fetal and neonatal rabbit heart. Mean values and standard error for each age group are given. The number of samples is indicated in parenthesis.

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Rdsumd. Chez le L a p i n n o u v e a u - n 6 , le t a u x de la n o r a d r 6 n a l i n e c a r d i a q u e s'616ve b r u s q u e m e n t , d o u b l a n t p r e s q u e p e n d a n t les 4 h e u r e s qui s u i v e n t la p a r t u r i t i o n .

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EPINEPHRINE n g / heart

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declines to 13 • 4 a t p a r t u r i t i o n . A f t e r 1 t o 4 h a n d e v e n a f t e r 3 days, t h e level still r e m a i n s v e r y low (10 • 2 a n d 11 • 1 ng/g). O n l y a s l i g h t c h a n g e was n o t i c e d w h e n t h e m e a n v a l u e s were e x p r e s s e d in rig/single h e a r t . Discussion. I t h a s b e e n s h o w n t h a t e n d o g e n o u s levels of c a t e c h o l a m i n e s are low in t h e f e t a l a n d n e w - b o r n a n i m a l s of some species 10-12. T h e c o n c e n t r a t i o n of c a r d i a c n o r e p i n e p h r i n e was f o u n d t o be low in t h e f e t a l p e r i o d (late t e r m ) a n d also a t p a r t u r i t i o n . A t a m o r e a d v a n c e d age ( 2 - 3 - d a y - o l d animals), t h e level w a s 8 0 % higher. This increase may be explained by a progressive maturat i o n of p o s t g a n g l i o n i c s y m p a t h e t i c i n n e r v a t i o n of t h e r a b b i t h e a r t . R e l a t i v e l y h i g h levels a t t a i n e d r a p i d l y w i t h i n 1 to 4 h a f t e r p a r t u r i t i o n c o u l d be d u e to a n increase in b i o s y n t h e s i s a n d also to u p t a k e . I n t h e a d r e n a l s of r a b b i t fetus, t h e c a t e c h o l a m i n e c o n c e n t r a t i o n rises p r o g r e s s i v e l y d u r i n g t h e 3rd t e r m of tile fetal p e r i o d ~ a n d declines t o a b o u t 5 0 % w i t h i n 4 h a f t e r p a r e u r i t i o n 2. P l a s m a n o r e p i n e p h r i n e level is h i g h a t p a r t u r i t i o n in n e w - b o r n r a b b i t s a n d decrease b e t w e e n 4 - 8 h a f t e r b i r t h ~. T h e h e a r t of t h e n e w - b o r n r a t a t t h e age of I t o 8 d a y s is u n a b l e to b i n d ~ H - n o r e p i n e p h r i n e as well as does t h e a d u l t h e a r t ~3. As no s i m i l a r r e s e a r c h h a s b e e n d o n e on t h e n e w - b o r n r a b b i t h e a r t , we do n o t k n o w e x a c t l y if a n d how much norepinephrine can be bound just after birth. I t is ,possible t h a t t h e n e w - b o r n r a b b i t h e a r t is able to t a k e up, a t l e a s t t e m p o r a r i l y , some of t h e n o r e p i n e p h r i n e p r e s e n t in t h e p l a s m a , w h i c h declines a f t e r p a r t u r i t i o n . If so, o n l y t h e n o r e p i n e p h r i n e was b o u n d a n d n o t t h e e p i n e p h r i n e , w h i c h does n o t increase in t h e h e a r t a f t e r birth. I t is n o t sure t h a t t h e r e l a t i v e l y h i g h c o n c e n t r a t i o n of n o r e p i n e p h r i n e f o u n d in t h e n e w - b o r n h e a r t w i t h i n 1 t o 4 h a f t e r p a r t u r i t i o n is a b s o l u t e l y n e c e s s a r y for its a c t i v i t y . I n t h e a d u l t a n i m a l s , t h e role p l a y e d b y endoge n o u s n o r e p i n e p h r i n e , e.g. on cardiac c o n t r a c t i l i t y , is still controversial~4. I t h a s b e e n suggested t h a t a d r e n a l release of c a t e c h o l a m i n e s in t h e n e w - b o r n a n i m a l s could p l a y a critical role in s t i m u l a t i n g t h e c a r d i o v a s c u l a r r e s p o n s e t o a s p h y x i a a n d i n i t i a t i n g r e s p i r a t i o n a t b i r t h 1~. T h e s u d d e n increase of c a r d i a c n o r e p i n e p h r i n e a few h o u r s a f t e r p a r t u r i t i o n s u p p o r t s t h i s h y p o t h e s i s t6

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Laboratoire d'Endocrinologie, Bdtiment 497, Universitd Paris X I , F 97405 Orsay (France), 26 J~ly 797~.

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L. L. IV~RSEN, J. DE CHAMPLAIN,J. GLOWINSKIand J. AXELROD, J. Pharmac. exp. Ther. J57, 509 (1967). n W. F. FRIEDMAN, P. E. PooL, D. JACOBOWITZ, S. C. GEAGREiqand E. BRAUNWALD,Circulation Res. 23, 25 (1967). 1 2 j. ROFFI, Ann. Endocr., Paris 29, 277 (1968). 1 3 J. GLO~VINSKI,J. AXELROD, I. J. I~OPIN and R. J. WURT~AN, J. Pharmac. exp. Ther. 7d6, 48 (1964). 14 j . F. SPANN, E. H. SONNENBLICK, T. COOPER, C. A. CHIDSEY, V. L. WILLMAN and E. BRAUNX~rALD,Circulation Res. 79, 317 (1966). 15 R. S. COMLINE and M. SILVER, J. Physiol., Loud. 183, 305 (1966). 1 6 This study was supported by a grant from DGRST (D614gation G6n6rale ~ la Reeherehe Scientifique et Technique, contrat No. 7173219). lo

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Fig. 2. Epinephrine level in fetal and neonatal rabbit heart (for legend, see Figure 1).