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The influence of calcium on the function-independent energy consumption (F.I.E.) of the isolated, isovolumically beating rabbit heart
56 rats r e l e a s e no or o n l y a v e r y small a m o u n t of p r o s tacyclin; in c o n t r o l rats this p r o d u c t i o n was about 3 n g . m i n - l . g -I. We c o n c l u d e t h a t d i e t a r y l i n o l e i c a c i d is e s s e n t i a l for p r o s t a c y c l i n p r o d u c t i o n of the rat h e a r t and, as p r o s t a c y c l i n has v a s o d i l a t i n g p r o p e r t i e s , may i n f l u e n c e c o r o n a r y flow. 1 D . H . N u g t e r e n et al.: This m e e t i n g ; a b s t r a c t p.35. 2 E.A.M. de Deckere, F. ten Hoor; This meeting, a b s t r a c t p.7.
91.
THE I N F L U E N C E OF C A L C I U M ON THE F U N C T I O N I N D E P E N D E N T E N E R G Y C O N S U M P T I O N (F.I.E]) OF THE ISOLATED, I S O V O L U M I C A L L Y B E A T I N G R A B B I T HEART. M. Theisohn, I n s t i t u t e of P h a r m a c o l o g y , U n i v e r s i t y of Cologne, W e s t Germany. The e n e r g y c o n s u m p t i o n of the isolated, isov o l u m i c a l l y b e a t i n g r a b b i t h e a r t was d e t e r m i n e d by s i m u l t a n e o u s m e a s u r e m e n t of m y o c a r d i a l h e a t p r o d u c tion and o x y g e n c o n s u m p t i o n . At d i f f e r e n t [Ca]o h e a r t f u n c t i o n was v a r i e d by s t e p w i s e i n c r e a s i n g the left i n t r a v e n t r i c u l a r v o l u m e (balloon catheter). The r e l a t i o n s h i p of d e v e l o p e d w a l l t e n s i o n to e n e r g y c o n s u m p t i o n was d e t e r m i n e d by linear r e g r e s s i o n analysis. A c c o r d i n g to Gibbs and G i b s o n (Cardiovasc. Res. 6, 508, 1972) F.I.E. was d e t e r m i n e d as the i n t e r c e p t of the r e g r e s s i o n line w i t h the ordinate. The r e d u c t i o n of [Ca]o f r o m 0.9 to 0.45 m M d e c r e a s e d F.I.E. by a b o u t 25%. At the same time, the m e a n d e v e l o p e d w a l l t e n s i o n was r e d u c e d by about 45%, i n d i c a t i n g that the a m o u n t of Ca ++ available for the a c t i v a t i o n of the c o n t r a c t i l e s y s t e m was d i m i n i s h e d c o n s i d e r a b l y . In c o n s e q u e n c e , a s m a l l e r a m o u n t of e n e r g y had to be spent for the s e q u e s t r a t i o n of these Ca ions, and F.I.E. was d e c r e a s e d . A b o l i s h i n g a l m o s t c o m p l e t e l y the contractions by the Ca a n t a g o n i s t V e r a p a m i l r e d u c e d the total e n e r g y c o n s u m p t i o n to about 40% of F.I.E. F r o m these data the e n e r g y c o n s u m p t i o n of the c a l c i u m t r a n s p o r t i n g p r o c e s s was c a l c u l a t e d to a m o u n t to 50% of the F.I.E.
91.
THE I N F L U E N C E OF C A L C I U M ON THE F U N C T I O N I N D E P E N D E N T E N E R G Y C O N S U M P T I O N (F.I.E]) OF THE ISOLATED, I S O V O L U M I C A L L Y B E A T I N G R A B B I T HEART. M. Theisohn, I n s t i t u t e of P h a r m a c o l o g y , U n i v e r s i t y of Cologne, W e s t Germany. The e n e r g y c o n s u m p t i o n of the isolated, isov o l u m i c a l l y b e a t i n g r a b b i t h e a r t was d e t e r m i n e d by s i m u l t a n e o u s m e a s u r e m e n t of m y o c a r d i a l h e a t p r o d u c tion and o x y g e n c o n s u m p t i o n . At d i f f e r e n t [Ca]o h e a r t f u n c t i o n was v a r i e d by s t e p w i s e i n c r e a s i n g the left i n t r a v e n t r i c u l a r v o l u m e (balloon catheter). The r e l a t i o n s h i p of d e v e l o p e d w a l l t e n s i o n to e n e r g y c o n s u m p t i o n was d e t e r m i n e d by linear r e g r e s s i o n analysis. A c c o r d i n g to Gibbs and G i b s o n (Cardiovasc. Res. 6, 508, 1972) F.I.E. was d e t e r m i n e d as the i n t e r c e p t of the r e g r e s s i o n line w i t h the ordinate. The r e d u c t i o n of [Ca]o f r o m 0.9 to 0.45 m M d e c r e a s e d F.I.E. by a b o u t 25%. At the same time, the m e a n d e v e l o p e d w a l l t e n s i o n was r e d u c e d by about 45%, i n d i c a t i n g that the a m o u n t of Ca ++ available for the a c t i v a t i o n of the c o n t r a c t i l e s y s t e m was d i m i n i s h e d c o n s i d e r a b l y . In c o n s e q u e n c e , a s m a l l e r a m o u n t of e n e r g y had to be spent for the s e q u e s t r a t i o n of these Ca ions, and F.I.E. was d e c r e a s e d . A b o l i s h i n g a l m o s t c o m p l e t e l y the contractions by the Ca a n t a g o n i s t V e r a p a m i l r e d u c e d the total e n e r g y c o n s u m p t i o n to about 40% of F.I.E. F r o m these data the e n e r g y c o n s u m p t i o n of the c a l c i u m t r a n s p o r t i n g p r o c e s s was c a l c u l a t e d to a m o u n t to 50% of the F.I.E.