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Xestospongin C, a Selective and Membrane-Permeable Inhibitor of IP(3) Receptor, Attenuates the Positive Inotropic Effect of Alpha-Adrenergic Stimulation in Guinea-Pig Papillary Muscle

Xestospongin C, a Selective and Membrane-Permeable Inhibitor of IP(3) Receptor, Attenuates the Positive Inotropic Effect of Alpha-Adrenergic Stimulation in Guinea-Pig Papillary Muscle

S Miyamoto, M Izumi, M Hori, M Kobayashi, H Ozaki, H Karaki

Br J Pharmacol. 2000 Jun;130(3):650-4.

PMID: 10821794

Abstract:

We evaluated the role of the inositol 1,4,5-triphosphate (IP(3)) receptor-mediated Ca(2+) release on the positive inotropic effects of alpha-adrenergic stimulation using a novel, potent, selective membrane-permeable blocker of IP(3) receptor, xestospongin C. Guinea-pig papillary muscle permeabilized with saponin exhibited spontaneous oscillatory contractions in solution buffered with pCa(2+) 6.5 by a low concentration of EGTA. The oscillatory activity was increased by adding 100 microM IP(3) and abolished by 1 microM ryanodine or 30 microM cyclopiazonic acid. Xestospongin C (3 microM) inhibited the IP(3)-induced increase in the oscillatory contractions without affecting basal oscillations. In intact papillary muscle, xestospongin C (3 microM) inhibited the positive inotropic effects of phenylephrine, resulting in a rightward and downward shift of the concentration-response curve for phenylephrine. On the contrary, xestospongin C did not affect the concentration-response curve for phenylephrine obtained in the presence of ryanodine (1 microM). On the other hand, xestospongin C affected neither basal contractions nor the positive inotropic effects of a high extracellular Ca(2+) concentration (3.2 mM) or that of isoprenaline (1 and 10 nM). These results suggest that the IP(3)-mediated increase in Ca(2+) release is involved in the positive inotropic effects of alpha-adrenergic stimulation in the guinea-pig cardiac muscle.

Chemicals Related in the Paper:

Catalog Number	Product Name	Structure	CAS Number	Price
AP88903699	Xestospongin C		88903-69-9	Price

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