752
Specialia
EXPERIENTIA 33/6
Extraction fraction at any urine flow and extraction percentage 1 J. T. B a k e r a n d C. P. C a i n
Department o[ Physiology and Bioengineering, Eastern Virginia Medical School, P. O. Box 1980, Nor/olk (Virginia 23501, USA), 6 December 7976 Summary. E x t r a c t i o n f r a c t i o n of r e n a l s o l u t e s is o r d i n a r i l y c a l c u l a t e d a s a r a t i o of a r t e r i a l a n d v e n o u s c o n c e n t r a t i o n d i f f e r e n c e s . C a l c u l a t i o n s p r o v i d e d in t h e p r e s e n t m a n u s c r i p t i l l u s t r a t e t h e n e e d t o c o r r e c t for c h a n g e s in r e n a l v e n o u s c o n c e n t r a t i o n w h e n s o l u t e e x t r a c t i o n is low a n d u r i n e flow s i m u l t a n e o u s l y h i g h . T h e extraction fraction used by renal physiologists in the e s t i m a t e of r e n a l p l a s m a flow, p e r f u s i o n of f u n c t i o n a l m a s s , a n d p e r c e n t a g e of p l a s m a flow f i l t e r e d is f o u n d in s t a n d a r d t e x t s of r e n a l p h y s i o l o g y 2-5. B y d e f i n i t i o n e x t r a c t i o n f r a c t i o n h a s b e e n c a l c u l a t e d as a r t e r i a l a n d v e n o u s c o n c e n t r a t i o n d i f f e r e n c e s of a n y s o l u t e u s e d t o m e a s u r e flow r a t e . T h u s Ax - Vx - 100 Ax
Ex
w h e r e E is e x t r a c t i o n , A t h e a r t e r i a l a n d V t h e v e n o u s c o n c e n t r a t i o n s of s o l u t e x. T h i s c a l c u l a t i o n a s s u m e s t h a t v e n o u s o u t f l o w e q u a l s a r t e r i a l inflow. O u r c a l c u l a t i o n s r e v e a l t h a t t h i s a s s u m p t i o n is t r u e o n l y w h e n e x t r a c t i o n of a s o l u t e is h i g h a n d w h e n u r i n e flow is s i m u l t a n e o u s l y minimal.
Calculations: B y o u r d e f i n i t i o n Ax Vx Ux Ra Rv Ru
= = = = = =
renal arterial concentration, mg/ml renal venous concentration, mg]ml urinary concentration, mg/ml renal arterial flow, ml/min renal venous flow, ml/min urinary flow, ml/min
T h e a m o u n t of s o l u t e e n t e r i n g t h e k i d n e y m u s t e q u a l t h e a m o u n t i n r e n a l v e n o u s b l o o d p l u s t h e a m o u n t in u r i n e . A x . Ra = V x . R v + U x . Ru
(1)
I n a d d i t i o n , v o l u m e flow in t h e r e n a l a r t e r y m u s t e q u a l t o t a l o u t f l o w , t h e s u m of r e n a l v e n o u s a n d u r i n e flow + lymph Ra = Rv + R u o r R v ~ R a - R u
(2)
Discussion. T h e p r e s e n t r e p o r t s h o w s t h a t u n d e r c e r t a i n conditions a s y s t e m a t i c error can be introduced into the c a l c u l a t i o n of e x t r a c t i o n f r a c t i o n . T h e s e c o n d i t i o n s inc l u d e a r e l a t i v e l y low s o l u t e e x t r a c t i o n a n d a s i m u l t a n e o u s l y large r e m o v a l of fluid f r o m t h e k i d n e y b y n o n v e n o u s r o u t e s . T h e s e a r e t a k e n t o b e u r i n e flow a n d lymphatic drainage. Previous data suggest that renal l y m p h a t i c d r a i n a g e e v e n u n d e r d i u r e t i c c o n d i t i o n s is less t h a n 1% of t o t a l r e n a l p l a s m a flow 6, ~. T h e r e f o r e , we h a v e n o t a d d e d t h i s t e r m to o u r e q u a t i o n s . L a r g e u r i n e v o l u m e s r e s u l t f r o m a v a r i e t y of c o n d i t i o n s , i n c l u d i n g p h a r m a c o l o g i c d i u r e s i s s a n d o s m o t i c d i u r e s i s 9. L o w solute e x t r a c t i o n s are generally seen w i t h s u b s t a n c e s n o t s e c r e t e d b y tile n e p h r o n , e.g., i n u l i n a n d c r e a t i n i n e . Under certain conditions, substances secreted by the k i d n e y w h i c h e x h i b i t h i g h e x t r a c t i o n ( > 80%) a t low p l a s m a c o n c e n t r a t i o n s e x h i b i t low r e n a l e x t r a c t i o n a t h i g h p l a s m a c o n c e n t r a t i o n s d u e t o s a t u r a t i o n of t h e s e c r e t o r y m e c h a n i s m , e.g., p a r a - a m i n o h i p p u r a t e . T h e s e
1 2 3 4
S u b s t i t u t i n g in t h e f i r s t e q u a t i o n A x - R a = V x ( R a - R u ) + U x . Ru
(3)
and re-arranging Ax. Ra-Vx (Ra-Ru) = Ux,Ru
(4)
U x 9 R u is t h e a m o u n t of s o l u t e x e x c r e t e d p e r u n i t t i m e . D i v i d i n g b o t h sides b y t h e a m o u n t e n t e r i n g t h e r e n a l artery Ux-Ru Ax. Ra-Vx (Ra-Ru) A x . Ra = Ax-Ra
5 6 7 8 9
Acknowledgments. This work was supported by Eastern Virginia Medical Authority and the Kidney Foundation of Tidewater, Virginia, USA. J . W . Bauman and F. P. Chinard, in: Renal Function: Physiological and Medical Aspects, p. 65. C. V. Mosley Co., St. Louis 1975. E.E. Bittar, in : Elements of Renal Physiology, p. 29. Am. Print. & Publ. Inc., Wisconsin 1974. H. Valtin, in: Renal Function: Mechanisms Preserving Fluid and Solute Balance in Health, p. 74. Little, Brown & Co, Boston 1973. A.V. Wolf, Am. J. Physiol. 133, 496 {1941). J. BergstrSm, H. Bucht, J. Ek, B. Josephson, H. Jundell and L. WerkS, Stand. J. olin. lab. Invest. /1, 361 (1959). Y . J . Katz, Circ. Res. 6, 452 (1958). L . E . Earley, J. A. Martino and R. M. Friedler, J. clin. Invest. 45, 1668 (1966). J . T . Baker and L. I. Kleinman, J. Physiol. 243, 45 (1974).
(5)
If E is t h e f r a c t i o n of s o l u t e X w h i c h is e x c r e t e d E
U x . Ru Ax - Vx (1 - Ru/Ra) = X 100 Ax 9 Ra Ax
Calculated percentage solute extracted 90.0 80.0 70.0 60.0 50.0 40 30
(6)
T h e t a b l e i l l u s t r a t e s t h e e r r o r s w h i c h will o c c u r w h e n s o l u t e e x t r a c t i o n is low a n d u r i n e f l o w s i m u l t a n e o u s l y is i n c r e a s e d . A s c a n be s e e n in t h i s t a b l e , w h e n t h e p e r c e n t a g e of s o l u t e e x t r a c t i o n is 9 0 % as d e t e r m i n e d b y t h e c o n v e n t i o n a l m e t h o d , c o r r e c t i o n for u r i n e flow r e s u l t s in little c h a n g e in t h e t r u e e x t r a c t i o n f r a c t i o n . H o w e v e r , u n d e r c o n d i t i o n s of b o t h low p e r c e n t a g e e x t r a c t i o n a n d h i g h flow r a t e , e x t r a c t i o n f r a c t i o n is c o n s i d e r a b l y u n d e r estimated. As extraction approaches 100% a n d urine flow a p p r o a c h e s zero, t h e o r i g i n a l f o r m u l a for e x t r a c t i o n f r a c t i o n m a y be e m p l o y e d w i t h m i n i m a l error.
Fraction of arterial plasma (Ru) water excreted ~ a True extraction percentage 0.01 0.05 0.10 0.15 0.20
90.1 90.5 91.0 91.5 92.0
80.2 81.0 82.0 83.0 84.0
70.3 71.5 73.0 74.5 76.0
60.4 62.0 64.0 66.0 68.0
50.5 52.5 55.0 57.5 60.0
40.6 43.0 46.0 49.0 52.0
30.7 33.5 37.0 40.5 44.0
Data are calculated to illustrate the error incurred in the determination of extraction fraction when urine flow is high and extraction percentage simultaneously low.
15.6. 1977
Specialia
s u b s t a n c e s are also p o o r l y e x t r a c t e d b y t h e i m m a t u r e k i d n e y l 0 , n a n d in diseases of t h e n e p h r o n 6. T h u s , a v a r i e t y of c o n d i t i o n s e x i s t w h i c h m a y b e a s s o c i a t e d w i t h errors in t h e c a l c u l a t i o n of e x t r a c t i o n f r a c t i o n . As m i g h t b e e x p e c t e d , v a r i a t i o n s in f i l t r a t i o n f r a c t i o n will affect t h e e r r o r in c a l c u l a t i o n of e x t r a c t i o n fraction. R e d u c t i o n of f i l t r a t i o n f r a c t i o n t e n d s t o r e d u c e e r r o r of c a l c u l a t e d e x t r a c t i o n f r a c t i o n b e c a u s e u r i n e flow is a lower f r a c t i o n of r e n a l a r t e r i a l flow. W o l f 5 o r i g i n a l l y s u g g e s t e d t h a t a c o r r e c t i o n for u r i n e flow was n e c e s s a r y for c a l c u l a t i o n of r e n a l p l a s m a flow. H i s calculations show a systematic error ranging from 4 to 14% d e p e n d i n g o n u r i n e flow. S o m e w h a t s i m i l a r errors (table) are e x p e c t e d for t h e c a l c u l a t i o n of e x t r a c t i o n fraction, d e p e n d i n g o n u r i n e flow a n d e x t e n t of solute e x t r a c t i o n . T h e following c a l c u l a t i o n shows t h e e r r o r i n c u r r e d w h e n c o r r e c t i o n for u r i n e flow is n o t m a d e in t h e c a l c u l a t i o n of e x t r a c t i o n fraction.
753
I n t h e n e w b o r n dog, R P F = 1.0 m l / m i n / g k i d n e y weight, G F R = 0.20 m l / m i n / g k i d n e y weight, a n d E x = 0.404. As r e p o r t e d i n t h e l i t e r a t u r e F . E . w a t e r m a y b e 5 0 % in c e r t a i n e x p e r i m e n t a l c o n d i t i o n s in t h i s species 9,12. T h u s , 0.20• = 0.10 m l / m i n / g k i d n e y weight. R u / R a = 0.10/1.0 = 10%. F r o m t h e t a b l e , E x is a c t u a l l y 0.46 n o t 0.40, a n e r r o r of 15%. T h i s e r r o r will b e c o m e g r e a t e r as u r i n e flow increases a n d solute e x t r a c t i o n is r e d u c e d - is.
10 M. Horster and H. Valtin, J. elin. Invest. 50, 779 (1971). U R . J . Lubbe and L. l. Kleinman, J. Physiol. 223, 411 (1972). 12 R.F. Pitts, in: Physiology of the Kidney and Body Fluids, 3rd ed., p. 159. Yearbook Medical Publishers, Chicago 1973. 13 L. G. Wesson, in: Physiology of the Human Kidney, p. 90. Grune and Stratton. New York 1969. \
D i s t r i b u t i o n of 14C after t o p i c a l a p p l i c a t i o n of 14C - l a b e l e d 1 , 3 - b i s - ( 2 - c h l o r o e t h y l ) 1 - n i t r o s o u r e a ( B C N U ) in m i c e H. S. Z a c k h e i m , R. J. F e l d m a n n , C. L i n d s a y a n d H. I. M a i b a c h 1
Department of Dermatology, University of California Medical Center, San Francisco (California 94743, USA), 17 October 7976 Summary. F o l l o w i n g t o p i c a l a p p l i c a t i o n of ~4C-labeled 1, 3 - b i s ( 2 - c h l o r o e t h y l ) - l - n i t r o s o u r e a (BCNU, c a r m u s t i n e ) t o t h e s k i n of mice r a d i o a c t i v i t y was f o u n d in all v i s c e r a a n d tissues ex~/mined. E x c l u s i v e of t h e gut, h i g h e s t v a l u e s were r e c o r d e d for t h e liver, k i d n e y a n d lung. Topically applied 1,3-bis(2-chloroethyl)- 1 - n i t r o s o u r e a (BCNU, c a r m u s t i n e ) is a n effective t r e a t m e n t for m y c o s i s fungoides 3. T h i s p a p e r r e p o r t s tile p a t t e r n of o r g a n a n d t i s s u e d i s t r i b u t i o n of I~C following t h e t o p i c a l a p p l i c a t i o n of 14C-labeled B C N U to m o u s e skin. E t h y l labeled 14CB C N U was s u p p l i e d b y W m . H. Y a n k o , M o n s a n t o R e search Corp., a t t h e r e q u e s t of D r V i n c e n t T. Oliverio, N a t i o n a l C a n c e r I n s t i t u t e . T h e specific a c t i v i t y of t h e s a m p l e was 10.07 m C i / m m o l e (47.06 txCi/mg) w i t h a r a d i o c h e m i c a l p u r i t y of 98.5%. T h e d o r s a l n e c k region of 7 f e m a l e Swiss mice, w e i g h t 32-43 g, was s h a v e d w i t h a n electric clippers 1 d a y p r i o r t o t h e a p p l i c a t i o n . 100 ~zl of 14C-BCNU in m e t h a n o l , 0.1062 m g (5 tzCi), was a p p l i e d to a 5 c m 2 s h a v e d a r e a a n d allowed t o d r y for 2 rain. As
Distribution of I~C after application of 14C-BCNU to mice~ Topical application of 106.2 [zg
Liver Kidney Lung Heart Spleen Brain Gut b Feces Muscle Fat
lh 3.72 3.13 1.60 1.15 1.08 0.53 3.94 3.95 0.70 0.41
2h 2.74 3.11 1.45 0.95 1.43 0.37 6.19o 0.56 0.16
3h 2.39 1.85 1.08 0.54 0.94 0.36 4.33 4.33 0.34 0.27
5h 1.50 1.14 0.70 0.39 0.70 0.31 1.42 3.06 0.21 0.17
6h 0.27 0.34 0.21 0.11 0.03 0.11 0.37 c 0.06 0.14
s.c. (21.2 ~g) 18h 0.22 0.31 0.18 0.12 0.19 0.11 0.13 0.22 0.05 0.03
24h 0.20 0.32 0.17 0.14 0.19 0.10 0.36 0.63 0.07 0.08
6h 0.30 0.47 0.27 0.14 0.05 0.13 0.46 1.96 0.22 0.17
9Expressed as [~g BCNU-equivalent per g organ or tissue, bEntire gastro-intestinal tract. Clncludes contents.
a c o n t r o l for possible i n g e s t i o n of t h e c o m p o u n d , 1 m o u s e was g i v e n 0.0212 m g (1 ~Ci) of 14C-BCNU in p r o p y l e n e glycol s.c. a n d sacrificed a f t e r 6 h. T h e mice were p l a c e d in i n d i v i d u a l h o l d i n g cages. F o o d a n d w a t e r were allowed ad libitum. T h e mice were sacrificed a t 1, 2, 3, 5, 6, 18 a n d 24 h b y cervical dislocation. Carcass w e i g h t s were d e t e r m i n e d , a n d t h e a n i m a l s were c a r e f u l l y dissected. T h e lung, h e a r t , liver, k i d n e y s , spleen, b r a i n , g u t (entire g a s t r o - i n t e s t i n a l t r a c t ) a n d pieces of m u s c l e a n d f a t were a n a l y z e d . A f t e r r e m o v a l e a c h t i s s u e was i m m e d i a t e l y p u t in a s e p a r a t e , p r e - w e i g h e d glass c o u n t i n g vial. U s i n g a 7 m l T e n B r o e c k t i s s u e h o m o genizer e a c h s a m p l e was h o m o g e n i z e d w i t h 10-15 m l distilled water. F o r a n a l y s i s of t h e 14C c o n t e n t a p u b l i s h e d m e t h o d was used 3. T h i s c o n s i s t e d of w e t a s h i n g a 2 m l s a m p l e of t h e h o m o g e n a t e w i t h 2 % p o t a s s i u m d i c h r o m a t e in c o n c e n t r a t e d sulfuric acid, a n d t r a p p i n g t h e e v o l v e d 14CO2 w i t h e t h a n o l a m i n e . T h i s was a d d e d t o a s c i n t i l l a t o r fluid a n d c o u n t e d w i t h a p p r o p r i a t e s t a n d a r d s in a B e c k m a n liquid s c i n t i l l a t i o n c o u n t e r . R e s u l t s were e x p r e s s e d in ~g of B C N U p e r g of o r g a n (wet weight), utilizing a c o m p u t e r p r o g r a m . B C N U is r a p i d l y d e g r a d e d following i.v. or oral a d m i n i s t r a t i o n 5. H e n c e t h e l~C a c t i v i t y m o s t likely r e p r e s e n t s f r a g m e n t s or m e t a b o l i c p r o d u c t s of t h e applied c o m p o u n d . T h e t a b l e s t a t e s t h e B C N U e q u i v a l e n t s in m o u s e o r g a n s a n d tissues, e x p r e s s e d in ~tg/g w e t weight, a f t e r a single a p p l i c a t i o n of 106.2 ~tg 14C-BCNU t o t h e s h a v e d skin, a n d 1 Supported by Public Health Service, grant CA 14825, from the National Cancer Institute, National Institutes of Health, Department of Health, Education and Welfare. 2 H.S. Zackheim, E. H. Epstein, Jr, Archs Derm. 117, 1564 (1975). 3 H . I . Maibach and R. J. Feldmann, Ann. N. Y. Acad. Sci. Idl, 423 (1967).
Specialia
EXPERIENTIA 33/6
Extraction fraction at any urine flow and extraction percentage 1 J. T. B a k e r a n d C. P. C a i n
Department o[ Physiology and Bioengineering, Eastern Virginia Medical School, P. O. Box 1980, Nor/olk (Virginia 23501, USA), 6 December 7976 Summary. E x t r a c t i o n f r a c t i o n of r e n a l s o l u t e s is o r d i n a r i l y c a l c u l a t e d a s a r a t i o of a r t e r i a l a n d v e n o u s c o n c e n t r a t i o n d i f f e r e n c e s . C a l c u l a t i o n s p r o v i d e d in t h e p r e s e n t m a n u s c r i p t i l l u s t r a t e t h e n e e d t o c o r r e c t for c h a n g e s in r e n a l v e n o u s c o n c e n t r a t i o n w h e n s o l u t e e x t r a c t i o n is low a n d u r i n e flow s i m u l t a n e o u s l y h i g h . T h e extraction fraction used by renal physiologists in the e s t i m a t e of r e n a l p l a s m a flow, p e r f u s i o n of f u n c t i o n a l m a s s , a n d p e r c e n t a g e of p l a s m a flow f i l t e r e d is f o u n d in s t a n d a r d t e x t s of r e n a l p h y s i o l o g y 2-5. B y d e f i n i t i o n e x t r a c t i o n f r a c t i o n h a s b e e n c a l c u l a t e d as a r t e r i a l a n d v e n o u s c o n c e n t r a t i o n d i f f e r e n c e s of a n y s o l u t e u s e d t o m e a s u r e flow r a t e . T h u s Ax - Vx - 100 Ax
Ex
w h e r e E is e x t r a c t i o n , A t h e a r t e r i a l a n d V t h e v e n o u s c o n c e n t r a t i o n s of s o l u t e x. T h i s c a l c u l a t i o n a s s u m e s t h a t v e n o u s o u t f l o w e q u a l s a r t e r i a l inflow. O u r c a l c u l a t i o n s r e v e a l t h a t t h i s a s s u m p t i o n is t r u e o n l y w h e n e x t r a c t i o n of a s o l u t e is h i g h a n d w h e n u r i n e flow is s i m u l t a n e o u s l y minimal.
Calculations: B y o u r d e f i n i t i o n Ax Vx Ux Ra Rv Ru
= = = = = =
renal arterial concentration, mg/ml renal venous concentration, mg]ml urinary concentration, mg/ml renal arterial flow, ml/min renal venous flow, ml/min urinary flow, ml/min
T h e a m o u n t of s o l u t e e n t e r i n g t h e k i d n e y m u s t e q u a l t h e a m o u n t i n r e n a l v e n o u s b l o o d p l u s t h e a m o u n t in u r i n e . A x . Ra = V x . R v + U x . Ru
(1)
I n a d d i t i o n , v o l u m e flow in t h e r e n a l a r t e r y m u s t e q u a l t o t a l o u t f l o w , t h e s u m of r e n a l v e n o u s a n d u r i n e flow + lymph Ra = Rv + R u o r R v ~ R a - R u
(2)
Discussion. T h e p r e s e n t r e p o r t s h o w s t h a t u n d e r c e r t a i n conditions a s y s t e m a t i c error can be introduced into the c a l c u l a t i o n of e x t r a c t i o n f r a c t i o n . T h e s e c o n d i t i o n s inc l u d e a r e l a t i v e l y low s o l u t e e x t r a c t i o n a n d a s i m u l t a n e o u s l y large r e m o v a l of fluid f r o m t h e k i d n e y b y n o n v e n o u s r o u t e s . T h e s e a r e t a k e n t o b e u r i n e flow a n d lymphatic drainage. Previous data suggest that renal l y m p h a t i c d r a i n a g e e v e n u n d e r d i u r e t i c c o n d i t i o n s is less t h a n 1% of t o t a l r e n a l p l a s m a flow 6, ~. T h e r e f o r e , we h a v e n o t a d d e d t h i s t e r m to o u r e q u a t i o n s . L a r g e u r i n e v o l u m e s r e s u l t f r o m a v a r i e t y of c o n d i t i o n s , i n c l u d i n g p h a r m a c o l o g i c d i u r e s i s s a n d o s m o t i c d i u r e s i s 9. L o w solute e x t r a c t i o n s are generally seen w i t h s u b s t a n c e s n o t s e c r e t e d b y tile n e p h r o n , e.g., i n u l i n a n d c r e a t i n i n e . Under certain conditions, substances secreted by the k i d n e y w h i c h e x h i b i t h i g h e x t r a c t i o n ( > 80%) a t low p l a s m a c o n c e n t r a t i o n s e x h i b i t low r e n a l e x t r a c t i o n a t h i g h p l a s m a c o n c e n t r a t i o n s d u e t o s a t u r a t i o n of t h e s e c r e t o r y m e c h a n i s m , e.g., p a r a - a m i n o h i p p u r a t e . T h e s e
1 2 3 4
S u b s t i t u t i n g in t h e f i r s t e q u a t i o n A x - R a = V x ( R a - R u ) + U x . Ru
(3)
and re-arranging Ax. Ra-Vx (Ra-Ru) = Ux,Ru
(4)
U x 9 R u is t h e a m o u n t of s o l u t e x e x c r e t e d p e r u n i t t i m e . D i v i d i n g b o t h sides b y t h e a m o u n t e n t e r i n g t h e r e n a l artery Ux-Ru Ax. Ra-Vx (Ra-Ru) A x . Ra = Ax-Ra
5 6 7 8 9
Acknowledgments. This work was supported by Eastern Virginia Medical Authority and the Kidney Foundation of Tidewater, Virginia, USA. J . W . Bauman and F. P. Chinard, in: Renal Function: Physiological and Medical Aspects, p. 65. C. V. Mosley Co., St. Louis 1975. E.E. Bittar, in : Elements of Renal Physiology, p. 29. Am. Print. & Publ. Inc., Wisconsin 1974. H. Valtin, in: Renal Function: Mechanisms Preserving Fluid and Solute Balance in Health, p. 74. Little, Brown & Co, Boston 1973. A.V. Wolf, Am. J. Physiol. 133, 496 {1941). J. BergstrSm, H. Bucht, J. Ek, B. Josephson, H. Jundell and L. WerkS, Stand. J. olin. lab. Invest. /1, 361 (1959). Y . J . Katz, Circ. Res. 6, 452 (1958). L . E . Earley, J. A. Martino and R. M. Friedler, J. clin. Invest. 45, 1668 (1966). J . T . Baker and L. I. Kleinman, J. Physiol. 243, 45 (1974).
(5)
If E is t h e f r a c t i o n of s o l u t e X w h i c h is e x c r e t e d E
U x . Ru Ax - Vx (1 - Ru/Ra) = X 100 Ax 9 Ra Ax
Calculated percentage solute extracted 90.0 80.0 70.0 60.0 50.0 40 30
(6)
T h e t a b l e i l l u s t r a t e s t h e e r r o r s w h i c h will o c c u r w h e n s o l u t e e x t r a c t i o n is low a n d u r i n e f l o w s i m u l t a n e o u s l y is i n c r e a s e d . A s c a n be s e e n in t h i s t a b l e , w h e n t h e p e r c e n t a g e of s o l u t e e x t r a c t i o n is 9 0 % as d e t e r m i n e d b y t h e c o n v e n t i o n a l m e t h o d , c o r r e c t i o n for u r i n e flow r e s u l t s in little c h a n g e in t h e t r u e e x t r a c t i o n f r a c t i o n . H o w e v e r , u n d e r c o n d i t i o n s of b o t h low p e r c e n t a g e e x t r a c t i o n a n d h i g h flow r a t e , e x t r a c t i o n f r a c t i o n is c o n s i d e r a b l y u n d e r estimated. As extraction approaches 100% a n d urine flow a p p r o a c h e s zero, t h e o r i g i n a l f o r m u l a for e x t r a c t i o n f r a c t i o n m a y be e m p l o y e d w i t h m i n i m a l error.
Fraction of arterial plasma (Ru) water excreted ~ a True extraction percentage 0.01 0.05 0.10 0.15 0.20
90.1 90.5 91.0 91.5 92.0
80.2 81.0 82.0 83.0 84.0
70.3 71.5 73.0 74.5 76.0
60.4 62.0 64.0 66.0 68.0
50.5 52.5 55.0 57.5 60.0
40.6 43.0 46.0 49.0 52.0
30.7 33.5 37.0 40.5 44.0
Data are calculated to illustrate the error incurred in the determination of extraction fraction when urine flow is high and extraction percentage simultaneously low.
15.6. 1977
Specialia
s u b s t a n c e s are also p o o r l y e x t r a c t e d b y t h e i m m a t u r e k i d n e y l 0 , n a n d in diseases of t h e n e p h r o n 6. T h u s , a v a r i e t y of c o n d i t i o n s e x i s t w h i c h m a y b e a s s o c i a t e d w i t h errors in t h e c a l c u l a t i o n of e x t r a c t i o n f r a c t i o n . As m i g h t b e e x p e c t e d , v a r i a t i o n s in f i l t r a t i o n f r a c t i o n will affect t h e e r r o r in c a l c u l a t i o n of e x t r a c t i o n fraction. R e d u c t i o n of f i l t r a t i o n f r a c t i o n t e n d s t o r e d u c e e r r o r of c a l c u l a t e d e x t r a c t i o n f r a c t i o n b e c a u s e u r i n e flow is a lower f r a c t i o n of r e n a l a r t e r i a l flow. W o l f 5 o r i g i n a l l y s u g g e s t e d t h a t a c o r r e c t i o n for u r i n e flow was n e c e s s a r y for c a l c u l a t i o n of r e n a l p l a s m a flow. H i s calculations show a systematic error ranging from 4 to 14% d e p e n d i n g o n u r i n e flow. S o m e w h a t s i m i l a r errors (table) are e x p e c t e d for t h e c a l c u l a t i o n of e x t r a c t i o n fraction, d e p e n d i n g o n u r i n e flow a n d e x t e n t of solute e x t r a c t i o n . T h e following c a l c u l a t i o n shows t h e e r r o r i n c u r r e d w h e n c o r r e c t i o n for u r i n e flow is n o t m a d e in t h e c a l c u l a t i o n of e x t r a c t i o n fraction.
753
I n t h e n e w b o r n dog, R P F = 1.0 m l / m i n / g k i d n e y weight, G F R = 0.20 m l / m i n / g k i d n e y weight, a n d E x = 0.404. As r e p o r t e d i n t h e l i t e r a t u r e F . E . w a t e r m a y b e 5 0 % in c e r t a i n e x p e r i m e n t a l c o n d i t i o n s in t h i s species 9,12. T h u s , 0.20• = 0.10 m l / m i n / g k i d n e y weight. R u / R a = 0.10/1.0 = 10%. F r o m t h e t a b l e , E x is a c t u a l l y 0.46 n o t 0.40, a n e r r o r of 15%. T h i s e r r o r will b e c o m e g r e a t e r as u r i n e flow increases a n d solute e x t r a c t i o n is r e d u c e d - is.
10 M. Horster and H. Valtin, J. elin. Invest. 50, 779 (1971). U R . J . Lubbe and L. l. Kleinman, J. Physiol. 223, 411 (1972). 12 R.F. Pitts, in: Physiology of the Kidney and Body Fluids, 3rd ed., p. 159. Yearbook Medical Publishers, Chicago 1973. 13 L. G. Wesson, in: Physiology of the Human Kidney, p. 90. Grune and Stratton. New York 1969. \
D i s t r i b u t i o n of 14C after t o p i c a l a p p l i c a t i o n of 14C - l a b e l e d 1 , 3 - b i s - ( 2 - c h l o r o e t h y l ) 1 - n i t r o s o u r e a ( B C N U ) in m i c e H. S. Z a c k h e i m , R. J. F e l d m a n n , C. L i n d s a y a n d H. I. M a i b a c h 1
Department of Dermatology, University of California Medical Center, San Francisco (California 94743, USA), 17 October 7976 Summary. F o l l o w i n g t o p i c a l a p p l i c a t i o n of ~4C-labeled 1, 3 - b i s ( 2 - c h l o r o e t h y l ) - l - n i t r o s o u r e a (BCNU, c a r m u s t i n e ) t o t h e s k i n of mice r a d i o a c t i v i t y was f o u n d in all v i s c e r a a n d tissues ex~/mined. E x c l u s i v e of t h e gut, h i g h e s t v a l u e s were r e c o r d e d for t h e liver, k i d n e y a n d lung. Topically applied 1,3-bis(2-chloroethyl)- 1 - n i t r o s o u r e a (BCNU, c a r m u s t i n e ) is a n effective t r e a t m e n t for m y c o s i s fungoides 3. T h i s p a p e r r e p o r t s tile p a t t e r n of o r g a n a n d t i s s u e d i s t r i b u t i o n of I~C following t h e t o p i c a l a p p l i c a t i o n of 14C-labeled B C N U to m o u s e skin. E t h y l labeled 14CB C N U was s u p p l i e d b y W m . H. Y a n k o , M o n s a n t o R e search Corp., a t t h e r e q u e s t of D r V i n c e n t T. Oliverio, N a t i o n a l C a n c e r I n s t i t u t e . T h e specific a c t i v i t y of t h e s a m p l e was 10.07 m C i / m m o l e (47.06 txCi/mg) w i t h a r a d i o c h e m i c a l p u r i t y of 98.5%. T h e d o r s a l n e c k region of 7 f e m a l e Swiss mice, w e i g h t 32-43 g, was s h a v e d w i t h a n electric clippers 1 d a y p r i o r t o t h e a p p l i c a t i o n . 100 ~zl of 14C-BCNU in m e t h a n o l , 0.1062 m g (5 tzCi), was a p p l i e d to a 5 c m 2 s h a v e d a r e a a n d allowed t o d r y for 2 rain. As
Distribution of I~C after application of 14C-BCNU to mice~ Topical application of 106.2 [zg
Liver Kidney Lung Heart Spleen Brain Gut b Feces Muscle Fat
lh 3.72 3.13 1.60 1.15 1.08 0.53 3.94 3.95 0.70 0.41
2h 2.74 3.11 1.45 0.95 1.43 0.37 6.19o 0.56 0.16
3h 2.39 1.85 1.08 0.54 0.94 0.36 4.33 4.33 0.34 0.27
5h 1.50 1.14 0.70 0.39 0.70 0.31 1.42 3.06 0.21 0.17
6h 0.27 0.34 0.21 0.11 0.03 0.11 0.37 c 0.06 0.14
s.c. (21.2 ~g) 18h 0.22 0.31 0.18 0.12 0.19 0.11 0.13 0.22 0.05 0.03
24h 0.20 0.32 0.17 0.14 0.19 0.10 0.36 0.63 0.07 0.08
6h 0.30 0.47 0.27 0.14 0.05 0.13 0.46 1.96 0.22 0.17
9Expressed as [~g BCNU-equivalent per g organ or tissue, bEntire gastro-intestinal tract. Clncludes contents.
a c o n t r o l for possible i n g e s t i o n of t h e c o m p o u n d , 1 m o u s e was g i v e n 0.0212 m g (1 ~Ci) of 14C-BCNU in p r o p y l e n e glycol s.c. a n d sacrificed a f t e r 6 h. T h e mice were p l a c e d in i n d i v i d u a l h o l d i n g cages. F o o d a n d w a t e r were allowed ad libitum. T h e mice were sacrificed a t 1, 2, 3, 5, 6, 18 a n d 24 h b y cervical dislocation. Carcass w e i g h t s were d e t e r m i n e d , a n d t h e a n i m a l s were c a r e f u l l y dissected. T h e lung, h e a r t , liver, k i d n e y s , spleen, b r a i n , g u t (entire g a s t r o - i n t e s t i n a l t r a c t ) a n d pieces of m u s c l e a n d f a t were a n a l y z e d . A f t e r r e m o v a l e a c h t i s s u e was i m m e d i a t e l y p u t in a s e p a r a t e , p r e - w e i g h e d glass c o u n t i n g vial. U s i n g a 7 m l T e n B r o e c k t i s s u e h o m o genizer e a c h s a m p l e was h o m o g e n i z e d w i t h 10-15 m l distilled water. F o r a n a l y s i s of t h e 14C c o n t e n t a p u b l i s h e d m e t h o d was used 3. T h i s c o n s i s t e d of w e t a s h i n g a 2 m l s a m p l e of t h e h o m o g e n a t e w i t h 2 % p o t a s s i u m d i c h r o m a t e in c o n c e n t r a t e d sulfuric acid, a n d t r a p p i n g t h e e v o l v e d 14CO2 w i t h e t h a n o l a m i n e . T h i s was a d d e d t o a s c i n t i l l a t o r fluid a n d c o u n t e d w i t h a p p r o p r i a t e s t a n d a r d s in a B e c k m a n liquid s c i n t i l l a t i o n c o u n t e r . R e s u l t s were e x p r e s s e d in ~g of B C N U p e r g of o r g a n (wet weight), utilizing a c o m p u t e r p r o g r a m . B C N U is r a p i d l y d e g r a d e d following i.v. or oral a d m i n i s t r a t i o n 5. H e n c e t h e l~C a c t i v i t y m o s t likely r e p r e s e n t s f r a g m e n t s or m e t a b o l i c p r o d u c t s of t h e applied c o m p o u n d . T h e t a b l e s t a t e s t h e B C N U e q u i v a l e n t s in m o u s e o r g a n s a n d tissues, e x p r e s s e d in ~tg/g w e t weight, a f t e r a single a p p l i c a t i o n of 106.2 ~tg 14C-BCNU t o t h e s h a v e d skin, a n d 1 Supported by Public Health Service, grant CA 14825, from the National Cancer Institute, National Institutes of Health, Department of Health, Education and Welfare. 2 H.S. Zackheim, E. H. Epstein, Jr, Archs Derm. 117, 1564 (1975). 3 H . I . Maibach and R. J. Feldmann, Ann. N. Y. Acad. Sci. Idl, 423 (1967).
