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KMID : 0351619720130020285
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Kyungpook Medical Journal
1972 Volume.13 No. 2 p.285 ~ p.290
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Effects of Calcium and Glucose on Negative Inotropic Action Induced by Changing on pH 7.4 to 6.5
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金重暎/Kim, Choong Young
李聲鎭/徐大圭/Lee, Sung Chin/Suh, Tae Kyu
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Abstract
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Many investigators have estabilshed that negative intoropic action induced by low pH of bathing media might be resulted from the inhibition of glycolysis, or of Cam+ release from sarcoplasmic reticulum system, that glycolysis in isolated atria would be affected by extracellular Ca++ concentration.
Our expeirments were taken to observe efi`ects of added glucose (5 m:ll) and Ca´+ as CaClz (2.44 mM) on the negative inotropic action induced by the omission of substrate at pH 7.4 and 6.5 and effects of added Ca++ on the negative inotropic action induced by the lowering of pH from 7.4 to 6.5 in glucose-Kreb´s Ringer bicarbonate buffer. As low as pH 6.5 was obtained by the decrease of HCO3-concentration from Kreb´s Ringer bicarbonate buffer with. or without glucose (glucose-KRB buffer and KRB buffer)
(1) Addition of glucose restored atrial cor.~tractility depressed by the omission of glucose from media, the restoration was more remarked atpH 7.4 than at pH 6.5 (Fig. I and II), and addition of CaClz, the restoration was as similar at pH 7.4 as at pH 6.5. (Fig.. II and III)
(2) Addition of CaClz restored atrial contractility depressed by lowering of pH from 7.4 to 6.5, percentage increase of contractility induced by added CaClz was more remarked at pH ~.4 than at 6.5 (Fig. II and III).
(3) CaClz-induced positive inotropic action in glucose-KRB was more remaked and prolonged than in KRB buffer, difference between the action of Ca++ in glucose-KRB and in KRB buffer at pH 7.4 was more remarkable than at pH 6.5 (Fig. II and Table I)
These results suggest that negative inotropic action induced by low pH of bathing media is likely to result from inhibition of estracellu]ar glucose utilization, but not to result from inhibition of extracellular Ca++ utilization, even if inhibition of intracellular Ca++ release from sarcoplasmic reticulum system might be related to the negative inotropic action.
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