Effects of isoprenaline and phenylephrine on energy‐rich phosphate compounds and glucose‐6‐phosphate in smooth and cardiac muscle

Abstract

1 Tension changes produced by phenylephrine and isoprenaline have been examined in four tissues—the guinea-pig taenia coli, the longitudinal muscle strip of rabbit duodenum, the abdominal aorta of the rabbit and the rat heart. 2 Changes in the amounts of adenosine triphosphate (ATP), creatine phosphate (CP) and glucose-6-phosphate (G-6-P) associated with the addition of phenylephrine and isoprenaline have been measured in the four tissues using enzymatic fluorimetric analysis. 3 An α-adrenoceptor-mediated increase in tension (phenylephrine; rabbit aorta) was associated with no change in the amounts of ATP, CP or G-6-P. 4 An α-adrenoceptor-mediated decrease in tension (phenylephrine; guinea-pig taenia coli and rabbit duodenum) was associated with no change in the amounts of ATP, CP or G-6-P. 5 A β-adrenoceptor-mediated increase in force of contraction (phenylephrine and isoprenaline; rat heart) was associated with a reduction in the amounts of ATP and CP and an increase in the amount of G-6-P. 6 A β-adrenoceptor-mediated decrease in tension (isoprenaline; guinea-pig taenia coli and rabbit duodenum) was associated with an increase in the amounts of ATP and CP and no change in the amount of G-6-P. 7 β-Adrenoceptor-mediated metabolic changes were antagonized by propranolol.