- Email: [email protected]
Neuropeptide-receptor interactions: With special reference to the VIP receptor(s)
140
Effects
B.
of PHI and V I P on n e u r o h y p o p h y s e a l
BARDRUM I,
J.
of Clin. Chem., 2Dept. of Ob/Gyn,
release.
FAHRENKRUG I,
B. OTTESEN I, A.-R. FUCHS 2. iDept. B i s p e b j e r g Hospital, Copenhagen D e n m a r k and Cornell University, Med. College, NY, NY, USA.
We h a v e p r e v i o u s l y shown that V I P causes the r e l e a s e of o x y t o c i n (OT) and v a s o p r e s s i n (AVP) w h e n i n f u s e d into the c e r e b r a l vent r i c l e (ICV). PHI d e r i v e s from the same p r e c u r s o r m o l e c u l e as V I P and has s i m i l a r properties. We, therefore, s t u d i e d the effcet of PHI g i v e n ICV on OT and A V P release. Blood was c o l l e c t e d from a n a e s t h e t i z e d rats b e f o r e and 5, 15, 30 and 60 m i n a f t e r the ICY i n f u s i o n of v a r y i n g doses (0.3 p m o l / k g x m i n to 3 n m o l / k g x min for 5 min) of PHI in 0.9% NaCl w i t h 0.5% HSA. A s i g n i f i c a n t inc r e a s e o v e r c o n t r o l OT and A V P levels was seen a f t e r ICV infusion of 3 n m o l / k g x min of PHI. Plasma O T rose m o r e r a p i d l y than AVP. It was i n c r e a s e d at 5 m i n and r e a c h e d p e a k levels (42 ± 6 ~U/ml) at 15 m i n w h e r e a s p l a s m a A V P did not rise until 15 m i n a f t e r PHI i n f u s i o n and r e a c h e d p e a k levels (87 ± 21 ~U/ml) at 30-60 min. In c o m p a r i s o n w i t h e q u i m o l a r infusions of VIP, PHI r e l e a s e d signific a n t l y less OT but more AVP; the e f f e c t of PHI on A V P a p p e a r e d to be of l o n g e r d u r a t i o n than the e f f e c t of VIP. W h e n b o t h p e p t i d e s w e r e g i v e n s i m u l t a n e o u s l y (a fixed dose of V I P w i t h i n c r e a s i n g d o s e s of PHI or v i c e versa), an i n t e r a c t i o n was seen only at the h i g h e s t dose level. 300 p m o l / k g x min PHI p o t e n t i a t e d the effect of 3 n m o l / k g x m i n V I P w h e r e a s 300 p m o l / k g x m i n V I P s u p p r e s s e d the e f f e c t of 3 n m o l / k g x m i n PHI on OT and A V P release. The r a p i d a c t i o n of PHI (and VIP), p a r t i c u l a r l y on OT r e l e a s e supports the h y p o t h e s i s that the a c t i o n of the p e p t i d e s is c e n t r a l rather than peripheral.
NEUROPEPTIDE-RECEPTOR INTERACTIONS: WITH SPECIAL REFERENCE TO THE VIP RECEPTOR(S) TAMAS BARTFAI Department o f Biochemistry, Arrhenius L a b o r a t o r i e s , U n i v e r s i t y of Stockholm, S-I06 91 Stockholm, Sweden The actions of peptide hormones on t a r g e t c e l l s are mediated by r e c e p t o r c o n t r o l l e d processes. The l i g a n d - r e c e p t o r i n t e r a c t i o n s f o r neuropeptide ligands have often been studied by l i m i t e d means as compared to s i m i l a r i n t e r actions f o r c l a s s i c a l n e u r o t r a n s m i t t e r s . These l i m i t a t i o n s stem from lack of s t a b i l e l i g a n d s , lack of u n i f o r m l y labeled l i g a n d s , lack o f large number of analogs with d i f f e r e n t i n t r i n s i c a c t i v i t y and most i m p o r t a n t l y from lack of high a f f i n i t y a n t a g o n i s t s . Research concerning the vasoactive i n t e s t i n a l polypeptide over the past 15 years has resolved many of these f o r peptide hormones c h a r a c t e r i s t i c problems. We have several studies on r a d i o l a b e l i n g , on b i o l o g i c a l s t a b i l i t y , on natural and s y n t h e t i c VIP analogs and fragments as VIP-receptor ligands and we even have VIP antagonists a v a i l a b l e . The VIP-receptor i t s e l f or at l e a s t one of the VIP-receptors is a member of the f a m i l y of G-protein l i n k e d receptors but i t s primary s t r u c t u r e has so f a r not been e l u c i d a t e d . VIP receptor numbers as well as the coupling of VIP receptors to e f f e c t o r molecules are subject to dynamic changes. In most tissues c o r r e l a t i o n between VIP receptor occupancy with agonists and s t i m u l a t i o n of the adenylate cyclase a c t i v i t y can be e s t a b l i s h e d .
Effects
B.
of PHI and V I P on n e u r o h y p o p h y s e a l
BARDRUM I,
J.
of Clin. Chem., 2Dept. of Ob/Gyn,
release.
FAHRENKRUG I,
B. OTTESEN I, A.-R. FUCHS 2. iDept. B i s p e b j e r g Hospital, Copenhagen D e n m a r k and Cornell University, Med. College, NY, NY, USA.
We h a v e p r e v i o u s l y shown that V I P causes the r e l e a s e of o x y t o c i n (OT) and v a s o p r e s s i n (AVP) w h e n i n f u s e d into the c e r e b r a l vent r i c l e (ICV). PHI d e r i v e s from the same p r e c u r s o r m o l e c u l e as V I P and has s i m i l a r properties. We, therefore, s t u d i e d the effcet of PHI g i v e n ICV on OT and A V P release. Blood was c o l l e c t e d from a n a e s t h e t i z e d rats b e f o r e and 5, 15, 30 and 60 m i n a f t e r the ICY i n f u s i o n of v a r y i n g doses (0.3 p m o l / k g x m i n to 3 n m o l / k g x min for 5 min) of PHI in 0.9% NaCl w i t h 0.5% HSA. A s i g n i f i c a n t inc r e a s e o v e r c o n t r o l OT and A V P levels was seen a f t e r ICV infusion of 3 n m o l / k g x min of PHI. Plasma O T rose m o r e r a p i d l y than AVP. It was i n c r e a s e d at 5 m i n and r e a c h e d p e a k levels (42 ± 6 ~U/ml) at 15 m i n w h e r e a s p l a s m a A V P did not rise until 15 m i n a f t e r PHI i n f u s i o n and r e a c h e d p e a k levels (87 ± 21 ~U/ml) at 30-60 min. In c o m p a r i s o n w i t h e q u i m o l a r infusions of VIP, PHI r e l e a s e d signific a n t l y less OT but more AVP; the e f f e c t of PHI on A V P a p p e a r e d to be of l o n g e r d u r a t i o n than the e f f e c t of VIP. W h e n b o t h p e p t i d e s w e r e g i v e n s i m u l t a n e o u s l y (a fixed dose of V I P w i t h i n c r e a s i n g d o s e s of PHI or v i c e versa), an i n t e r a c t i o n was seen only at the h i g h e s t dose level. 300 p m o l / k g x min PHI p o t e n t i a t e d the effect of 3 n m o l / k g x m i n V I P w h e r e a s 300 p m o l / k g x m i n V I P s u p p r e s s e d the e f f e c t of 3 n m o l / k g x m i n PHI on OT and A V P release. The r a p i d a c t i o n of PHI (and VIP), p a r t i c u l a r l y on OT r e l e a s e supports the h y p o t h e s i s that the a c t i o n of the p e p t i d e s is c e n t r a l rather than peripheral.
NEUROPEPTIDE-RECEPTOR INTERACTIONS: WITH SPECIAL REFERENCE TO THE VIP RECEPTOR(S) TAMAS BARTFAI Department o f Biochemistry, Arrhenius L a b o r a t o r i e s , U n i v e r s i t y of Stockholm, S-I06 91 Stockholm, Sweden The actions of peptide hormones on t a r g e t c e l l s are mediated by r e c e p t o r c o n t r o l l e d processes. The l i g a n d - r e c e p t o r i n t e r a c t i o n s f o r neuropeptide ligands have often been studied by l i m i t e d means as compared to s i m i l a r i n t e r actions f o r c l a s s i c a l n e u r o t r a n s m i t t e r s . These l i m i t a t i o n s stem from lack of s t a b i l e l i g a n d s , lack of u n i f o r m l y labeled l i g a n d s , lack o f large number of analogs with d i f f e r e n t i n t r i n s i c a c t i v i t y and most i m p o r t a n t l y from lack of high a f f i n i t y a n t a g o n i s t s . Research concerning the vasoactive i n t e s t i n a l polypeptide over the past 15 years has resolved many of these f o r peptide hormones c h a r a c t e r i s t i c problems. We have several studies on r a d i o l a b e l i n g , on b i o l o g i c a l s t a b i l i t y , on natural and s y n t h e t i c VIP analogs and fragments as VIP-receptor ligands and we even have VIP antagonists a v a i l a b l e . The VIP-receptor i t s e l f or at l e a s t one of the VIP-receptors is a member of the f a m i l y of G-protein l i n k e d receptors but i t s primary s t r u c t u r e has so f a r not been e l u c i d a t e d . VIP receptor numbers as well as the coupling of VIP receptors to e f f e c t o r molecules are subject to dynamic changes. In most tissues c o r r e l a t i o n between VIP receptor occupancy with agonists and s t i m u l a t i o n of the adenylate cyclase a c t i v i t y can be e s t a b l i s h e d .