Regulation by calcium of arachidonic acid metabolism in the isolated perfused rabbit heart

M. T. Weis, Kafait Malik

Research output: Contribution to journalArticle

9 Citations (Scopus)

Abstract

Activation of β-adrenergic receptors with isoproterenol fails to stimulate prostaglandin synthesis in the isolated rabbit heart perfused with Ca2+-free Krebs-Henseleit buffer. This lack of response could be due to reduced isoproterenol-stimulated liberation of arachidonic acid, reduced cyclooxygenase activity during Ca2+-free perfusion, or both. To test these hypotheses, we have examined the effect of isoproterenol and exogenous arachidonic acid on prostaglandin output in hearts perfused with Ca2+-containing and nominally Ca2+-free Krebs-Henseleit buffer. In hearts prelabelled with [3H]arachidonic acid and perfused with nominally Ca2+-free buffer, the release of radioactivity following isoproterenol was about 90% less than when Ca2+ was included in the perfusion buffer. When exogenous arachidonic acid was administered to hearts perfused with Ca2+-depleted buffer, the output of both 6-keto-prostaglandin F(1α) and prostaglandin E2 was about threefold greater than when Ca2+ was present in the perfusion medium. In the absence of Ca2+, the dose response curve for arachidonic acid-induced 6-keto-prostaglandin F(1α) synthesis underwent a parallel shift to the left, with no change in maximal synthesis levels, and a tenfold reduction in the ED50 of arachidonic acid. The cyclooxygenase activities of cell-free homogenates prepared from hearts perfused with and without Ca2+ were not different from each other and were both insensitive to added Ca2+. Reduction of the Na+ concentration of the perfusion medium to 35 mM resulted in increases in arachidonic acid-induced 6-keto-prostaglandin F(1α) less than those obtained during Ca2+-free perfusion, but greater than that observed during perfusion with normal Na+ (139 mM) and Ca2+ (2.5 mM). Arachidonic acid induced 6-keto-prostaglandin F(1α) output was inversely correlated with tissue Ca2+ but not Na+ content. These data suggest that in the absence of perfusate Ca2+, the availability of exogenous arachidonic acid to cyclooxygenase is increased, possibly by reduced incorporation into tissue phospholipids.

Original languageEnglish (US)
Pages (from-to)694-703
Number of pages10
JournalCirculation Research
Volume59
Issue number6
DOIs
StatePublished - Jan 1 1986

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Arachidonic Acid
Rabbits
Calcium
Perfusion
Prostaglandins F
Isoproterenol
Prostaglandin-Endoperoxide Synthases
Buffers
Prostaglandins
Dinoprostone
Adrenergic Receptors
Radioactivity
Phospholipids

All Science Journal Classification (ASJC) codes

  • Physiology
  • Cardiology and Cardiovascular Medicine

Cite this

Regulation by calcium of arachidonic acid metabolism in the isolated perfused rabbit heart. / Weis, M. T.; Malik, Kafait.

In: Circulation Research, Vol. 59, No. 6, 01.01.1986, p. 694-703.

Research output: Contribution to journalArticle

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abstract = "Activation of β-adrenergic receptors with isoproterenol fails to stimulate prostaglandin synthesis in the isolated rabbit heart perfused with Ca2+-free Krebs-Henseleit buffer. This lack of response could be due to reduced isoproterenol-stimulated liberation of arachidonic acid, reduced cyclooxygenase activity during Ca2+-free perfusion, or both. To test these hypotheses, we have examined the effect of isoproterenol and exogenous arachidonic acid on prostaglandin output in hearts perfused with Ca2+-containing and nominally Ca2+-free Krebs-Henseleit buffer. In hearts prelabelled with [3H]arachidonic acid and perfused with nominally Ca2+-free buffer, the release of radioactivity following isoproterenol was about 90{\%} less than when Ca2+ was included in the perfusion buffer. When exogenous arachidonic acid was administered to hearts perfused with Ca2+-depleted buffer, the output of both 6-keto-prostaglandin F(1α) and prostaglandin E2 was about threefold greater than when Ca2+ was present in the perfusion medium. In the absence of Ca2+, the dose response curve for arachidonic acid-induced 6-keto-prostaglandin F(1α) synthesis underwent a parallel shift to the left, with no change in maximal synthesis levels, and a tenfold reduction in the ED50 of arachidonic acid. The cyclooxygenase activities of cell-free homogenates prepared from hearts perfused with and without Ca2+ were not different from each other and were both insensitive to added Ca2+. Reduction of the Na+ concentration of the perfusion medium to 35 mM resulted in increases in arachidonic acid-induced 6-keto-prostaglandin F(1α) less than those obtained during Ca2+-free perfusion, but greater than that observed during perfusion with normal Na+ (139 mM) and Ca2+ (2.5 mM). Arachidonic acid induced 6-keto-prostaglandin F(1α) output was inversely correlated with tissue Ca2+ but not Na+ content. These data suggest that in the absence of perfusate Ca2+, the availability of exogenous arachidonic acid to cyclooxygenase is increased, possibly by reduced incorporation into tissue phospholipids.",
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N2 - Activation of β-adrenergic receptors with isoproterenol fails to stimulate prostaglandin synthesis in the isolated rabbit heart perfused with Ca2+-free Krebs-Henseleit buffer. This lack of response could be due to reduced isoproterenol-stimulated liberation of arachidonic acid, reduced cyclooxygenase activity during Ca2+-free perfusion, or both. To test these hypotheses, we have examined the effect of isoproterenol and exogenous arachidonic acid on prostaglandin output in hearts perfused with Ca2+-containing and nominally Ca2+-free Krebs-Henseleit buffer. In hearts prelabelled with [3H]arachidonic acid and perfused with nominally Ca2+-free buffer, the release of radioactivity following isoproterenol was about 90% less than when Ca2+ was included in the perfusion buffer. When exogenous arachidonic acid was administered to hearts perfused with Ca2+-depleted buffer, the output of both 6-keto-prostaglandin F(1α) and prostaglandin E2 was about threefold greater than when Ca2+ was present in the perfusion medium. In the absence of Ca2+, the dose response curve for arachidonic acid-induced 6-keto-prostaglandin F(1α) synthesis underwent a parallel shift to the left, with no change in maximal synthesis levels, and a tenfold reduction in the ED50 of arachidonic acid. The cyclooxygenase activities of cell-free homogenates prepared from hearts perfused with and without Ca2+ were not different from each other and were both insensitive to added Ca2+. Reduction of the Na+ concentration of the perfusion medium to 35 mM resulted in increases in arachidonic acid-induced 6-keto-prostaglandin F(1α) less than those obtained during Ca2+-free perfusion, but greater than that observed during perfusion with normal Na+ (139 mM) and Ca2+ (2.5 mM). Arachidonic acid induced 6-keto-prostaglandin F(1α) output was inversely correlated with tissue Ca2+ but not Na+ content. These data suggest that in the absence of perfusate Ca2+, the availability of exogenous arachidonic acid to cyclooxygenase is increased, possibly by reduced incorporation into tissue phospholipids.

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