May 1, 1989

125I-iodopindolol binding to frog esophageal peptic cells. Detection of amine uptake and beta-adrenergic receptors coupled to pepsinogen secretion

Biochemical Pharmacology
K E DickinsonB I Hirschowitz

Abstract

The beta-adrenergic receptors (beta-ARs) coupled to pepsinogen secretion on frog esophageal peptic cells have been compared to frog erythrocyte beta-ARs using the radioligand 125I-iodopindolol (125I-PIN). 125I-PIN binding to intact peptic cells was time and temperature dependent. Saturation and competition experiments established that a large component of this binding represented radioligand uptake, which was energy dependent, pH sensitive, Na+ independent, and inhibited by agents that depress cellular ATP or disrupt proton gradients. This uptake system, which was absent from frog erythrocytes, appeared similar to that recently described for a number of mammalian cells. 125I-PIN bound to a single class of sites on peptic cell homogenates with a KD = 64 (+/- 5) pM. Binding to cell homogenates and a proportion of the binding to intact cells was inhibited by beta-agonists and antagonists with pharmacological characteristics similar to typical beta 2-ARs of frog erythrocytes. The number of beta-ARs in these peptic cell preparations was 1300 (+/- 240) sites/cell. Isolated peptic cells were poorly responsive to isoproterenol stimulation even in the presence of the phosphodiesterase inhibitor IBMX (3-isobutyl-1-methylxanthine). Pretre...Continue Reading

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Citations

Mentioned in this Paper

Pepsinogen B
Visken
Epinephrine Acetate
Medihaler-Epi
Novodrin
3-iodopindolol, (-)-isomer
Beta-adrenergic receptor
Biogenic Amines
Tetradecanoylphorbol Acetate, 4a alpha-Isomer
Rana catesbeiana

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