Down-regulation of alpha 2-adrenoceptor subtypes.
To characterize further the alpha 2-adrenoceptor subtypes in terms of their regulation, monolayers of cells expressing either the alpha 2A (CHO-A2AR cells) or alpha 2C (OK cells) subtype were preincubated with norepinephrine for various times and the extent of receptor down-regulation was assessed. Exposure to 30 microM norepinephrine caused a similar time course and extent of down-regulation (approximately 50%) in both cells lines. The extent of down-regulation caused by 0.3 microM norepinephrine in OK cells was similar to that with 30 microM norepinephrine in CHO-A2AR cells, although the time course was somewhat slower. Reversal of the down-regulation of the alpha 2-adrenoceptor caused by 30 microM norepinephrine was more rapid in the CHO-A2AR than in the OK cell. With 0.3 microM norepinephrine, reversal of down-regulation of the alpha 2-adrenoceptor in the OK cell was slightly faster than that of the CHO-A2AR cell with 30 microM norepinephrine. These data indicate that although norepinephrine is more potent in causing down-regulation of the alpha 2C (OK cells) as compared to the alpha 2A subtype (CHO-A2AR cells), the time courses for down-regulation and its reversal are similar for the two subtypes.
Department of Pharmacology, University of Nebraska Medical Center, Omaha 68198-6260.
R C
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Pleus
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Shreve
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Toews
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Bylund
D000818:Animals; D016466:CHO Cells; D002460:Cell Line; D006224:Cricetinae; D003412:Cricetulus; D015536:Down-Regulation / Q000502:physiology*; D009638:Norepinephrine / Q000037:antagonists & inhibitors; D009893:Opossums; D011869:Radioligand Assay; D011942:Receptors, Adrenergic, alpha / Q000502:physiology*
D011942:Receptors, Adrenergic, alpha; D009638:Norepinephrine