title: Increase in potassium release from rat parotid tissue repeatedly exposed to isoproterenol.
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.
mesh_terms: D000818:Animals; D003513:Cycloheximide / Q000494:pharmacology; D003609:Dactinomycin / Q000494:pharmacology; D066298:In Vitro Techniques; D007545:Isoproterenol / Q000494:pharmacology*; D008297:Male; D010306:Parotid Gland / Q000187:drug effects* / Q000378:metabolism; D011188:Potassium / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D013565:Sympatholytics / Q000494:pharmacology; D013997:Time Factors
chemical_list: D013565:Sympatholytics; D003609:Dactinomycin; D003513:Cycloheximide; D007545:Isoproterenol; D011188:Potassium