Differential expression of ionic channels in rat anterior pituitary cells.
Secretory anterior pituitary cells are of the same origin, but exhibit cell type-specific patterns of spontaneous intracellular Ca2+ signaling and basal hormone secretion. To understand the underlying ionic mechanisms mediating these differences, we compared the ionic channels expressed in somatotrophs, lactotrophs, and gonadotrophs from randomly cycling female rats under identical cell culture and recording conditions. Our results indicate that a similar group of ionic channels are expressed in each cell type, including transient and sustained voltage-gated Ca2+ channels, tetrodotoxin-sensitive Na+ channels, transient and delayed rectifying K+ channels, and multiple Ca2+ -sensitive K+ channel subtypes. However, there were marked differences in the expression levels of some of the ionic channels. Specifically, lactotrophs and somatotrophs exhibited low expression levels of tetrodotoxin-sensitive Na+ channels and high expression levels of the large-conductance, Ca2+ -activated K+ channel compared with those observed in gonadotrophs. In addition, functional expression of the transient K+ channel was much higher in lactotrophs and gonadotrophs than in somatotrophs. Finally, the expression of the transient voltage-gated Ca2+ channels was higher in somatotrophs than in lactotrophs and gonadotrophs. These results indicate that there are cell type-specific patterns of ionic channel expression, which may be of physiological significance for the control of Ca2+ homeostasis and secretion in unstimulated and receptor-stimulated anterior pituitary cells.
Van Goor
F
F
Endocrinology and Reproduction Research Branch, National Institute of Child Health and Human Development, National Institutes of Health Bethesda, Maryland 20892-4510, USA.
Zivadinovic
D
D
Stojilkovic
S S
SS
D000818:Animals; D002118:Calcium / Q000494:pharmacology; D015220:Calcium Channels / Q000235:genetics; D002478:Cells, Cultured; D004594:Electrophysiology; D005260:Female; D015870:Gene Expression; D006065:Gonadotropins, Pituitary / Q000378:metabolism; D013006:Growth Hormone / Q000378:metabolism; D006801:Humans; D015640:Ion Channel Gating / Q000502:physiology; D007473:Ion Channels / Q000235:genetics*; D010903:Pituitary Gland, Anterior / Q000378:metabolism*; D015221:Potassium Channels / Q000235:genetics; D011388:Prolactin / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D015222:Sodium Channels / Q000235:genetics; D013779:Tetrodotoxin / Q000494:pharmacology
D015220:Calcium Channels; D006065:Gonadotropins, Pituitary; D007473:Ion Channels; D015221:Potassium Channels; D015222:Sodium Channels; D013779:Tetrodotoxin; D011388:Prolactin; D013006:Growth Hormone; D002118:Calcium