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KMID : 0370019910050000101
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Chung-Ang Journal of Pharmacal Sciences
1991 Volume.5 No. 0 p.101 ~ p.108
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Effects of calcium on the glucose release induced by alpha-and beta- adrenergic agonists and cAMP in perfused rat liver
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Abstract
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This study was performed to veify the role of Ca^++ and cAMP and interaction between phenylephrine and isoproterenol on hepatic glucose release in perfused rat liver.
The results are as follows.
1. In 1.3mM Ca^++ -contained perfusate, phenylephrine induced Ca^++ -efflux. Ca^++ -efflux by phynylephrine alone was higher than by the combination of phenlyphrine and isoproterenol or dibutyryl cyclic AMP(Bu_2cAMP). Additionally, Bu_2cAMP caused Ca^++ -influx, whereas isoproterenol showed no net change in Ca^++ -fluxes.
2. Phenylephrine didn´t increase glucose release in EGTA-treated buffer. The amount of glucose release was the highest in Ca^++ -contained buffer.
3. The increase of glucose release by isoproterenol or Bu_2cAMP in Ca^++ -contained buffer was less than in Ca^++ -free of EGTA-treated buffer.
4. The synergistic effect on glucose release was found by the combination of phenylephrine and isoproternol as well as by the combination of phenylephrine and Bu_2cAMP regardless of cellular Ca^++ level. The effect by simultaneous adminitstration was highest in Ca^++ -free buffer.
Therefore, it is concluded that phenylephrine requires Ca^++ to increase glucose release, but the effects of isoproterenol and Bu_2cAMP on hepatic glucose release are unrelated to cellulatr Ca^++. Bu_2cAMP inhibits Ca^++ -efflux induced by phenylephrine and acts synergistically with phenylephrine of hepatic glucose release.
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