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Voltage‐activated Ca 2+ channels and their role in the endocrine function of the pituitary gland in newborn and adult mice
Author(s) -
Sedej Simon,
Tsujimoto Tetsuhiro,
Zorec Robert,
Rupnik Marjan
Publication year - 2004
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1113/jphysiol.2003.058271
Subject(s) - exocytosis , endocrinology , medicine , secretion , pituitary gland , endocrine system , hormone , chemistry , biology
We have prepared fresh pituitary gland slices from adult and, for the first time, from newborn mice to assess modulation of secretory activity via voltage‐activated Ca 2+ channels (VACCs). Currents through VACCs and membrane capacitance have been measured with the whole‐cell patch‐clamp technique. Melanotrophs in newborns were significantly larger than in adults. In both newborn and adult melanotrophs activation of VACCs triggered exocytosis. All pharmacologically isolated VACC types contributed equally to the secretory activity. However, the relative proportion of VACCs differed between newborns and adults. In newborn cells L ‐type channels dominated and, in addition, an exclusive expression of a toxin‐resistant R‐type‐like current was found. The expression of L ‐type VACCs was up‐regulated by the increased oestrogen levels observed in females, and was even more emphasized in the cells of pregnant females and oestrogen‐treated adult male mice. We suggest a general mechanism modulating endocrine secretion in the presence of oestrogen and particularly higher sensitivity to treatments with L ‐type channel blockers during high oestrogen physiological states.