Phospholipid methylation in canine cardiac membranes. Relations to .BETA.-adrenergic receptors and digitalis receptors. : Relations to β-Adrenergic Receptors and Digitalis Receptors

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Phospholipid methylation of canine cardiac membranes was studied in vitro to determine its relationship to the regulation and function of β-adrenergic and digitalis receptors. Cardiac membranes were prepared from the left ventricle of mongrel dogs. Phospholipid methylation was assayed by measuring [3H] methyl incorporation after incubation with methyl donor S-adenosyl-L-[methyl-3H] methione at 37°C. The reaction of phospholipid methylation had an optimum pH around 9 and a linear time course of up to 60min. The reaction was inhibited by the addition of S-adenosyl-L-homocysteine, a known antagonist of biological transmethylation. L-isoproterenol enhanced phospholipid methylation markedly, but ouabain had no effect. On the other hand, after phospholipid methylation in cardiac membranes was stimulated by pre-incubation with S-adenosyl-L-methionine for 60min at 37°C, [125I] iodohydroxybenzylpindolol binding to the membranes was increased. The number of the β-adrenergic receptor binding sites (Bmax), calculated from Scatchard analysis in cardiac membranes of 3 dogs significantly increased. On the other hand, [3H] ouabain binding and Na+, K+, Mg2+-ATPase activity were not increased. The increase in [125I] iodohydroxybenzylpindolol binding was inhibited by the addition of S-adenosyl-L-homocysteine. These findings suggest that phospholipid methylation is closely related to β-adrenergic receptors, but not digitalis receptors in cardiac membranes.
International Heart Journal刊行会の論文

Phospholipid methylation in canine cardiac membranes. Relations to .BETA.-adrenergic receptors and digitalis receptors. : Relations to β-Adrenergic Receptors and Digitalis Receptors

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