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Functional Asymmetry in Phosphate Transport and Its Regulation in Opossum Kidney Cells: Parathyroid Hormone Inhibition by Stephan J. Reshkin; Judith Forgo; Heini Murer is a Medicine article available to read on EtoBox.

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The sidedness (apical vs basolateral) of the inhibitory of phosphate (Pi) transport by parathyroid hormone (PTH) was investigated in opossum kidney (OK)cell monolayers grown on permeant support. PTH was found to regulate the activity of only the apical Na/Pi cotransporter, having no effect on the basolateral transport systems. Transport inhibition was approximately 100fold more sensitive to apical PTH application (Kd: 5x10 -12 M) than to basolateral application (Kd: 5 x 10-1 o M). The time-course of the inhibitory response was identical from the two cell surfaces, with halfmaximum inhibition occurring at about 20 rain and almost full inhibition by 90 min. Experiments on diffusion and degradation demonstrated that the difference in Kd at the two cell surfaces was not due to differential metabolism or diffusion. Tests of cooperativity between the apical and basolateral regulatory events at intermediate concentrations suggested that the presence of PTH on one side of the monolayer reduced the scope of response from the other side. At maximum doses of PTH (10-7 \_ I0-8 M) the transport inhibition from either side was equal and not additive. We conclude that in OK-cell monolayers grown

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Author

Stephan J. Reshkin; Judith Forgo; Heini Murer

Publisher

Springer; Springer-Verlag; Springer Verlag; Springer Science and Business Media LLC (ISSN 0031-6768)

Published

1990

Language

EN

Field

Medicine (Life Sciences)