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POTENTIATION OF K+‐EVOKED CATECHOLAMINE RELEASE IN THE CAT ADRENAL GLAND TREATED WITH OUABAIN
Author(s) -
GARCIA A.G.,
GARCIALOPEZ E.,
HORGA J.F.,
KIRPEKAR S.M.,
MONTIEL C.,
SANCHEZGARCIA P.
Publication year - 1981
Publication title -
british journal of pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.432
H-Index - 211
eISSN - 1476-5381
pISSN - 0007-1188
DOI - 10.1111/j.1476-5381.1981.tb10478.x
Subject(s) - ouabain , catecholamine , endocrinology , medicine , chemistry , extracellular , tetraethylammonium , bicarbonate , intracellular , biology , sodium , biochemistry , potassium , organic chemistry
1 A vigorous catecholamine secretory response was evoked by small increments (2–10 mM) of the extracellular concentration of K + ([K + ]) 0 ) in cat adrenal glands treated with ouabain (10 −4 m), and perfused with Krebs‐bicarbonate solution at room temperature. 2 The secretory response depends on [K + ] 0 ; increments of [K + ] 0 as small as 2 mM for 2 min evoked a clear secretory response; at 10–17.7 mM K + , the maximal secretory response was observed. In normal glands, not treated with ouabain, no increase of the rate of catecholamine output was observed by raising [K + ]0 up to 17.7 mM for 2 min. 3 The K + secretory response was time‐dependent, requiring at least 1 min to be initiated; on continued exposure to 10 mM [K + ] 0 , the enhanced response remained for at least 1 h. 4 In low [Na + ] 0 , the K + ‐secretory response was unchanged. However, in 0‐Ca 2+ , high‐Mg 2+ solutions, or in the presence of D600, an organic Ca 2+ antagonist, it was abolished. 5 The K + ‐induced secretory response was not altered in the presence of tetrodotoxin or tetraethylammonium. 6 It is concluded that ouabain potentiated the catecholamine secretory response to raised [K + ] D by increasing the amount of Ca 2+ available to the secretory machinery through (a) mobilization of an enhanced pool of membrane‐bound Ca 2+ , (b) activation of membrane Ca 2+ inward current; or (c) decrease of intracellular Ca 2+ buffering systems. The activation by ouabain of a membrane Na + ‐Ca 2+ exchange system is not involved in this K + ‐secretory response. It is suggested that the plasma membrane ATPase enzyme system, by changing the affinity of its Ca 2+ binding sites, might control the availability of this cation to the secretory machinery and, therefore, modulate catecholamine secretion in the adrenal gland.