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  • Title: Isoproterenol potentiates alpha-adrenergic and muscarinic receptor-mediated Ca2+ response in rat parotid cells.
    Author: Tanimura A, Nezu A, Tojyo Y, Matsumoto Y.
    Journal: Am J Physiol; 1999 Jun; 276(6):C1282-7. PubMed ID: 10362590.
    Abstract:
    The effects of the cAMP pathway on the Ca2+ response elicited by phospholipase C-coupled receptor stimulations were studied in rat parotid cells. Although 1 microM isoproterenol (Iso) itself had no effect on the cytosolic Ca2+ concentration, the pretreatment with Iso potentiated Ca2+ responses evoked by phenylephrine. The potentiating effect of Iso was attributed to a shifting of the concentration-response curves of phenylephrine to the left and an increase in the maximal response. Half-maximal potentiation occurred at 3 nM Iso. Iso also potentiated the Ca2+ response elicited by carbachol. The potentiating effect of Iso was mimicked by forskolin (10 microM) and dibutyryl adenosine 3',5'-cyclic monophosphate (2 mM) and was blocked by 10 microM H-89. Iso potentiated the phenylephrine-induced Ca2+ response in the absence of extracellular Ca2+, but Iso did not increase the inositol trisphosphate (IP3) production induced by phenylephrine. These results suggest that the potentiation of the Ca2+ response can be attributed to a sensitization of IP3 receptors by cAMP-dependent protein kinase.
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