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Measurement of cholecystokinin octapeptide using a new specific radioimmunoassay
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M E A S U R E M E N T OF C H O L E C Y S T O K I N I N RADIOIMMUNOASSAY
OCTAPEPTIDE
USING A N E W SPECIFIC
A d r i a n T E, B a c a r e s e - H a m i l t o n A J and B l o o m S R Royal P o s t g r a d u a t e M e d i c a l School, Du Cane Road,
London W12 OHS
The C - t e r m i n a l o c t a p e p t i d e (CCK-8) is r e p o r t e d to be the most abundant form of c h o l e c y s t o k i n i n in tissues and in the circulation. Assays for C C K either c r o s s - r e a c t with larger m o l e c u l a r forms of CCK or with gastrins. No specific assay for the b i o l o g i c a l l y active CCK-8 form has h i t h e r t o been described. A p e p t i d e analogue of CCK-8 (tyroc), with tyrosine in place of the C - T e r m i n a l amide, was used both for iodination and for r a i s i n g antisera. Immunisation, u s i n g tyroc c o n j u g a t e d to a l b u m i n with b i s - d i a z o t i s e d benzidine, p r o d u c e d antisera d i r e c t e d towards the N - t e r m i n a l end of CCK-8. The label was p r o d u c e d by trace iodination, u s i n g c h l o r a m i n e T oxidation, f o l l o w e d by p u r i f i c a t i o n on high r e s o l u t i o n reverse phase HPLC. The assay appears t o t a l l y specific for the s u l p h a t e d C C K - 8 m o l e c u l e a n d shows no c r o s s - r e a c t i o n with n o n - s u l p h a t e d CCK-8, C - t e r m i n a l h e p t a p e p t i d e , larger forms of C C K or the gastrins. C h a n g e s b e t w e e n adjacent tubes at 0.25 fmol CCK-8 are d e t e c t a b l e with 95% confidence. In aqueous extracts of human b r a i n there was a good c o r r e l a t i o n b e t w e e n a c o n v e n t i o n a l C - t e r m i n a l C C K assay and this N - t e r m i n a l assay (R=0.98, N=30) R e v e r s e p h a s e HPLC of aqueous extracts of brain and gut r e v e a l e d a m a j o r p e a k in the p o s i t i o n of the synthetic CCK-8 s t a n d a r d and a minor early peak in the p o s i t i o n of o x i d i s e d CCK-8. The assay is robust, reliable and r e p r o d u c i b l e and can be used to m e a s u r e tissue and p l a s m a C C K - 8 levels.
PYY INFUSION
IN MAN - C I R C U L A T O R Y
AND G A S T R O I N T E S T I N A L
EFFECTS
A d r i a n T E, S a g o r G R, Savage A P, B a c a r e s e - H a m i l t o n A J, P o l a k J M a n d Bloom S R R o y a l P o s t g r a d u a t e M e d i c a l School,
Du Cane Road,
L o n d o n W12 OHS
PYY is a newly d i s c o v e r e d peptide, localised to endocrine cells of the i n t e s t i n a l m u c o s a and p a r t i c u l a r l y a b u n d a n t in the colon. The p h y s i o l o g i c a l role of PYY is unknown, but p h a r m a c o l o g i c a l studies in the cat have d e m o n s t r a t e d a v a s o c o n s t r i c t o r action and i n h i b i t i o n of p a n c r e a t i c secretion. The effects of a low dose of this candidate gut h o r m o n e w e r e t h e r e f o r e a s s e s s e d in man. PYY was i n f u s e d at a dose of 1 p m o l / k g / m i n w h i c h caused an increase in p l a s m a PYY c o n c e n t r a t i o n s of 79 • 7 p m o l / l (mean + SEM). During PYY systolic and diastolic b l o o d p r e s s u r e rose b y 8.6 • 3.7 m m Hg a n d 10.9 3.0 ~n H g r e s p e c t i v e l y (p < 0.05). PYY h a d no effect on secretin and C C K - 8 s t i m u l a t e d p a n c r e a t i c secretion. In contrast however, PYY c a u s e d a s u b s t a n t i a l r e d u c t i o n in p e n t a g a s t r i n s t i m u l a t e d gastric acid and p e p s i n secretin (52 + 6% fall d u r i n g PYY, p < 0.005). PYY a l s o s i g n i f i c a n t l y r e d u c e d c i r c u l a t i n g c o n c e n t r a t i o n s of p a n c r e a t i c p o l y p e p t i d e and m o t i l i n . In addition to its action as a v a s o c o n s t r i c t o r PYY s h o u l d now be c o n s i d e r e d as one of the p o s s i b l e factors in classical e n t e r o g a s t r o n e . The r e d u c t i o n of p l a s m a PP a n d m o t i l i n c o n c e n t r a t i o n s during P Y Y i n f u s i o n s u g g e s t that this p e p t i d e m a y also e x h i b i t p o t e n t motor actions in the h u m a n g a s r o i n t e s t i n a l tract .
M E A S U R E M E N T OF C H O L E C Y S T O K I N I N RADIOIMMUNOASSAY
OCTAPEPTIDE
USING A N E W SPECIFIC
A d r i a n T E, B a c a r e s e - H a m i l t o n A J and B l o o m S R Royal P o s t g r a d u a t e M e d i c a l School, Du Cane Road,
London W12 OHS
The C - t e r m i n a l o c t a p e p t i d e (CCK-8) is r e p o r t e d to be the most abundant form of c h o l e c y s t o k i n i n in tissues and in the circulation. Assays for C C K either c r o s s - r e a c t with larger m o l e c u l a r forms of CCK or with gastrins. No specific assay for the b i o l o g i c a l l y active CCK-8 form has h i t h e r t o been described. A p e p t i d e analogue of CCK-8 (tyroc), with tyrosine in place of the C - T e r m i n a l amide, was used both for iodination and for r a i s i n g antisera. Immunisation, u s i n g tyroc c o n j u g a t e d to a l b u m i n with b i s - d i a z o t i s e d benzidine, p r o d u c e d antisera d i r e c t e d towards the N - t e r m i n a l end of CCK-8. The label was p r o d u c e d by trace iodination, u s i n g c h l o r a m i n e T oxidation, f o l l o w e d by p u r i f i c a t i o n on high r e s o l u t i o n reverse phase HPLC. The assay appears t o t a l l y specific for the s u l p h a t e d C C K - 8 m o l e c u l e a n d shows no c r o s s - r e a c t i o n with n o n - s u l p h a t e d CCK-8, C - t e r m i n a l h e p t a p e p t i d e , larger forms of C C K or the gastrins. C h a n g e s b e t w e e n adjacent tubes at 0.25 fmol CCK-8 are d e t e c t a b l e with 95% confidence. In aqueous extracts of human b r a i n there was a good c o r r e l a t i o n b e t w e e n a c o n v e n t i o n a l C - t e r m i n a l C C K assay and this N - t e r m i n a l assay (R=0.98, N=30) R e v e r s e p h a s e HPLC of aqueous extracts of brain and gut r e v e a l e d a m a j o r p e a k in the p o s i t i o n of the synthetic CCK-8 s t a n d a r d and a minor early peak in the p o s i t i o n of o x i d i s e d CCK-8. The assay is robust, reliable and r e p r o d u c i b l e and can be used to m e a s u r e tissue and p l a s m a C C K - 8 levels.
PYY INFUSION
IN MAN - C I R C U L A T O R Y
AND G A S T R O I N T E S T I N A L
EFFECTS
A d r i a n T E, S a g o r G R, Savage A P, B a c a r e s e - H a m i l t o n A J, P o l a k J M a n d Bloom S R R o y a l P o s t g r a d u a t e M e d i c a l School,
Du Cane Road,
L o n d o n W12 OHS
PYY is a newly d i s c o v e r e d peptide, localised to endocrine cells of the i n t e s t i n a l m u c o s a and p a r t i c u l a r l y a b u n d a n t in the colon. The p h y s i o l o g i c a l role of PYY is unknown, but p h a r m a c o l o g i c a l studies in the cat have d e m o n s t r a t e d a v a s o c o n s t r i c t o r action and i n h i b i t i o n of p a n c r e a t i c secretion. The effects of a low dose of this candidate gut h o r m o n e w e r e t h e r e f o r e a s s e s s e d in man. PYY was i n f u s e d at a dose of 1 p m o l / k g / m i n w h i c h caused an increase in p l a s m a PYY c o n c e n t r a t i o n s of 79 • 7 p m o l / l (mean + SEM). During PYY systolic and diastolic b l o o d p r e s s u r e rose b y 8.6 • 3.7 m m Hg a n d 10.9 3.0 ~n H g r e s p e c t i v e l y (p < 0.05). PYY h a d no effect on secretin and C C K - 8 s t i m u l a t e d p a n c r e a t i c secretion. In contrast however, PYY c a u s e d a s u b s t a n t i a l r e d u c t i o n in p e n t a g a s t r i n s t i m u l a t e d gastric acid and p e p s i n secretin (52 + 6% fall d u r i n g PYY, p < 0.005). PYY a l s o s i g n i f i c a n t l y r e d u c e d c i r c u l a t i n g c o n c e n t r a t i o n s of p a n c r e a t i c p o l y p e p t i d e and m o t i l i n . In addition to its action as a v a s o c o n s t r i c t o r PYY s h o u l d now be c o n s i d e r e d as one of the p o s s i b l e factors in classical e n t e r o g a s t r o n e . The r e d u c t i o n of p l a s m a PP a n d m o t i l i n c o n c e n t r a t i o n s during P Y Y i n f u s i o n s u g g e s t that this p e p t i d e m a y also e x h i b i t p o t e n t motor actions in the h u m a n g a s r o i n t e s t i n a l tract .