Biophysical basis of pituitary cell type-specific Ca2+ signaling-secretion coupling.
All secretory pituitary cells exhibit spontaneous and extracellular Ca2+-dependent electrical activity. Somatotrophs and lactotrophs fire plateau-bursting action potentials, which generate Ca2+ signals of sufficient amplitude to trigger hormone release. Gonadotrophs also fire action potentials spontaneously, but as single, high-amplitude spikes with limited ability to promote Ca2+ influx and secretion. However, Ca2+ mobilization in gonadotrophs transforms single spiking into plateau-bursting-type electrical activity and triggers secretion. Patch clamp analysis revealed that somatotrophs and lactotrophs, but not gonadotrophs, express BK (big)-type Ca2+-controlled K+ channels, activation of which is closely associated with voltage-gated Ca2+ influx. Conversely, pituitary gonadotrophs express SK (small)-type Ca2+-activated K+ channels that are colocalized with intracellular Ca2+ release sites. Activation of both channels is crucial for plateau-bursting-type rhythmic electrical activity and secretion.
Stojilkovic
Stanko S
SS
Section on Cellular Signaling, Endocrinology and Reproduction Research Branch, National Institute of Child Health and Human Development, National Institutes of Health, MD 20892-4510, USA. stankos@helix.nih.gov
Zemkova
Hana
H
Van Goor
Fredrick
F
D000200:Action Potentials / Q000502:physiology; D000818:Animals; D055592:Biophysical Phenomena; D001703:Biophysics; D015220:Calcium Channels / Q000502:physiology; D020013:Calcium Signaling / Q000502:physiology*; D006801:Humans; D010902:Pituitary Gland / Q000166:cytology / Q000378:metabolism / Q000502:physiology*; D015221:Potassium Channels / Q000502:physiology; D015222:Sodium Channels / Q000502:physiology
D015220:Calcium Channels; D015221:Potassium Channels; D015222:Sodium Channels