Metabolic consequences of positive inotropy in rat and guinea-pig hearts.
The metabolic and physiological responses of hearts from male rats and guinea-pigs to isoprenaline and SK&F 94120 (a phosphodiesterase III inhibitor), have been studied. Doses which gave similar chronotropic stimulation gave different inotropic responses. In both species, isoprenaline generated a greater increase in developed tension than SK&F 94120. With both drugs the inotropic response in the rat was less than than in the guinea-pig. 31P-NMR investigation of high-energy phosphate levels showed reduction in PCr concentration and an accompanying acidosis in the isoprenaline-perfused rat heart only. In both species, lactate production was stimulated by SK&F 94120 but not by isoprenaline. These results are discussed with reference to G-protein activation of ion channels and differences in Ca2+ handling by the two species.
Kemp
P R
PR
Department of Biochemistry, University of Oxford, U.K.
Seymour
A M
AM
Bailey
I A
IA
Radda
G K
GK
D000138:Acidosis / Q000378:metabolism; D000818:Animals; D055598:Chemical Phenomena; D002621:Chemistry; D000242:Cyclic AMP / Q000378:metabolism; D006168:Guinea Pigs; D006321:Heart / Q000187:drug effects*; D006339:Heart Rate / Q000187:drug effects; D007545:Isoproterenol / Q000494:pharmacology; D007773:Lactates / Q000378:metabolism; D009682:Magnetic Resonance Spectroscopy; D008297:Male; D009206:Myocardium / Q000378:metabolism*; D010477:Perfusion; D010710:Phosphates / Q000378:metabolism; D011719:Pyrazines / Q000494:pharmacology; D051381:Rats
D007773:Lactates; D010710:Phosphates; D011719:Pyrazines; C048350:5-(4-acetamidophenyl)pyrazin-2(1H)-one; D000242:Cyclic AMP; D007545:Isoproterenol