| Autor: |
Tzour, A., Sosial, E., Meir, T., Canello, T., Naveh‐Many, T., Gabizon, R., Nussinovitch, I. |
| Předmět: |
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| Zdroj: |
Journal of Neuroendocrinology; Jan2013, Vol. 25 Issue 1, p76-86, 11p, 1 Color Photograph, 1 Black and White Photograph, 3 Charts, 5 Graphs |
| Abstrakt: |
The present study demonstrates that a significant proportion of high voltage-activated ( HVA) Ca2+ influx in native rat anterior pituitary cells is carried through non- L-type Ca2+ channels. Using whole-cell patch-clamp recordings and specific Ca2+ channel toxin blockers, we show that approximately 35% of the HVA Ca2+ influx in somatotrophs and lactotrophs is carried through Cav2.1, Cav2.2 and Cav2.3 channels, and that somatotrophs and lactotrophs share similar proportions of these non- L-type Ca2+ channels. Furthermore, experiments on mixed populations of native anterior pituitary cells revealed that the fraction of HVA Ca2+ influx carried through these non- L-type Ca2+ channels might even be higher (approximately 46%), suggesting that non- L-type channels exist in the majority of native anterior pituitary cells. Using western blotting, immunoblots for α1C, α1D, α1A, α1B and α1E Ca2+ channel subunits were identified in native rat anterior pituitary cells. Additionally, using reverse transcriptase-polymerase chain reaction, c DNA transcripts for α1C, α1D, α1A and α1B Ca2+ channel subunits were identified. Transcripts for α1E were nonspecific and transcripts for α1S were not detected at all (control). Taken together, these results clearly demonstrate the existence of multiple HVA Ca2+ channels in the membrane of rat native anterior pituitary cells. Whether these channels are segregated among different membrane compartments was investigated further in flotation assays, demonstrating that Cav2.1, Cav1.2 and caveolin-1 were mostly localised in light fractions of Nycodenz gradients (i.e. in lipid raft domains). Cav1.3 channels were distributed among both light and heavy fractions of the gradients (i.e. among raft and nonraft domains), whereas Cav2.2 and Cav2.3 channels were distributed mostly among nonraft domains. In summary, in the present study, we demonstrate multiple pathways for HVA Ca2+ influx through L-type and non- L-type Ca2+ channels in the membrane of native anterior pituitary cells. The compartmentalisation of these channels among raft and nonraft membrane domains might be essential for their proper regulation by separate receptors and signalling pathways. [ABSTRACT FROM AUTHOR] |
| Databáze: |
Complementary Index |
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