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  • Title: Increase in potassium release from rat parotid tissue repeatedly exposed to isoproterenol.
    Author: Ohshika H, Miyamoto A, Takemura H, Hatta S, Tanaka M.
    Journal: Jpn J Pharmacol; 1983 Aug; 33(4):811-7. PubMed ID: 6632381.
    Abstract:
    The effect of repeated exposure to isoproterenol (ISO) in parotid tissue was investigated with regards to potassium release in response to a successive challenge of alpha- and beta-adrenergic agonists. An increase in potassium release by epinephrine was potentiated in the parotid tissue from rats repeatedly administered ISO (3 mg/kg, three times daily for 3 days). On the other hand, a decrease in the release by ISO disappeared in ISO-pretreated glands. Cycloheximide and actinomycin D, administered with ISO, completely blocked the ISO-induced development of the enhanced response to epinephrine, but not that of the reduced response to ISO. After in vitro pretreatment with ISO, the potassium release induced by a successive dose of ISO was higher than the basal release of the electrolyte. The same treatment showed a tendency to increase the response to norepinephrine. The increased release induced by a challenge dose of ISO disappeared in the tissue from cycloheximide-treated rats. The ISO-induced increase of potassium release which was caused by ISO-pretreatment in vitro was inhibited by prazosin, but not by yohimbin and propranolol. These results suggest the possibility that the alpha-adrenergic response in parotid tissue might be potentiated by exposure to ISO.
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