Kappa-opioid peptide receptor stimulation increases cytosolic pH and myofilament responsiveness to Ca2+ in cardiac myocytes.
Although kappa- and delta-opioid receptors on mammalian cardiac myocytes have been discovered recently, the intracellular effects that result from stimulation of these receptors remain unknown. We examine the effects of a rapid and brief exposure to a kappa-opioid receptor agonist on intracellular Ca2+, pH, and cell length in individual isolated rat ventricular cells. The specific kappa-agonist trans-dl-3,4-dichloro-N-methyl-N-[2-(1-pyrrolidinyl)cyclohexyl]- benzene-acetamide (U-50488H) (methane sulfonate salt) caused a transient increase in cytosolic pH (pHi) measured from the change in SNARF-1 fluorescence and an increase in cytosolic [Ca2+] (Cai), indexed by a change in indo-1 fluorescence. The initial Cai increase often was followed by Cai oscillations. Both pHi and Cai effects were blocked by the specific antagonist kappa-opioid receptor l-(N-furylmethyl)-alpha-normetazocine methane-sulfonate (Mr 1452). The amplitude of contraction that accompanied the Cai increase elicited by U-50488H was greater than that associated with a similar increase in Cai elicited by electrical stimulation or by the rapid exposure of cells to caffeine. Thus an acute and brief kappa-opioid receptor stimulation of cardiac cells leads to an increase in Cai and pHi. The pHi increase was abolished by 1) blockade of the Na(+)-H+ exchanger by ethyl isopropyl amiloride and 2) inhibition of protein kinase C (PKC) activity via pretreatment with staurosporine or prolonged incubation with 4 beta-phorbol 12-myristate 13-acetate. These maneuvers did not abolish the U-50488H-induced increase in Ca.(ABSTRACT TRUNCATED AT 250 WORDS)
Ventura
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Laboratory of Cardiovascular Science, National Institute on Aging, National Institutes of Health, Baltimore, Maryland 21224.
Capogrossi
M C
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Spurgeon
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HA
Lakatta
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EG
D019900:3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; D000700:Analgesics / Q000494:pharmacology*; D000818:Animals; D001575:Benzomorphans / Q000494:pharmacology*; D002118:Calcium / Q000494:pharmacology*; D003600:Cytosol / Q000378:metabolism; D006321:Heart / Q000187:drug effects / Q000502:physiology*; D006863:Hydrogen-Ion Concentration; D066298:In Vitro Techniques; D007700:Kinetics; D009206:Myocardium / Q000378:metabolism; D009292:Narcotic Antagonists / Q000494:pharmacology*; D011759:Pyrrolidines / Q000494:pharmacology*; D011957:Receptors, Opioid / Q000187:drug effects / Q000502:physiology*; D017473:Receptors, Opioid, kappa; D013050:Spectrometry, Fluorescence
D000700:Analgesics; D001575:Benzomorphans; D009292:Narcotic Antagonists; D011759:Pyrrolidines; D011957:Receptors, Opioid; D017473:Receptors, Opioid, kappa; D019900:3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; C029552:Mr 1452; D002118:Calcium