Voltage-activated Ca(2+) channels and their role in the endocrine function of the pituitary gland in newborn and adult mice.
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.
Sedej
Simon
S
European Neuroscience Institute Göttingen, Waldweg 33, 37073 Göttingen, Germany.
Tsujimoto
Tetsuhiro
T
Zorec
Robert
R
Rupnik
Marjan
M
D000375:Aging / Q000502:physiology*; D000818:Animals; D000831:Animals, Newborn / Q000254:growth & development / Q000502:physiology*; D001464:Barium / Q000502:physiology; D015220:Calcium Channels / Q000502:physiology*; D020746:Calcium Channels, L-Type / Q000502:physiology; D004553:Electric Conductivity; D004967:Estrogens / Q000502:physiology; D005260:Female; D066298:In Vitro Techniques; D008297:Male; D009074:Melanocyte-Stimulating Hormones / Q000378:metabolism; D051379:Mice; D010902:Pituitary Gland / Q000166:cytology / Q000378:metabolism*; D011247:Pregnancy; D020033:Protein Isoforms / Q000502:physiology
D015220:Calcium Channels; D020746:Calcium Channels, L-Type; D004967:Estrogens; D020033:Protein Isoforms; D001464:Barium; D009074:Melanocyte-Stimulating Hormones