Voltage dependent calcium channels in adrenal glomerulosa cells and in insulin producing cells.
We have examined the structure and function of Ca2+ channels in excitable endocrine cell types, in rat adrenal glomerulosa cells and in two insulin producing cell types, the rat pancreatic beta cell and the INS-1 cell line. In previous studies on glomerulosa cells, we observed low (T-type) and high threshold (L-type) voltage dependent Ca2+ currents in addition to a K+ induced inward rectifying Ca2+ current (Igl). beta cells are known to exhibit T-, L- and N-type currents. We have now found that INS-1 cells also show low threshold (T-type) and high threshold Ca2+ currents. The latter was further resolved by organic inhibitors into L-type and P/Q-type currents and no Igl was detected. The expression of the pore-forming alpha 1 subunit of voltage dependent Ca2+ channels was studied by means of reverse transcription-polymerase chain reaction (RT-PCR), followed by restriction enzyme mapping and/or sequencing. Both in glomerulosa and pancreatic beta cells, the neuroendocrine (D) class of the alpha 1 subunit, known to be responsible for L-type current, represents the majority of the PCR product. Comparable amounts of the neuroendocrine (D) and the neuronal A-type alpha 1 subunits dominate the message in INS-1 cells. Different characteristics of Ca2+ currents in these cell types is discussed in view of the channel repertoire.
Horváth
A
A
Department of Physiology and Laboratory of Cellular and Molecular Physiology, Semmelweis University of Medicine, Budapest, Hungary.
Szabadkai
G
G
Várnai
P
P
Arányi
T
T
Wollheim
C B
CB
Spät
A
A
Enyedi
P
P
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D015220:Calcium Channels / Q000235:genetics* / Q000378:metabolism*; D020864:Calcium Channels, N-Type; D003001:Cloning, Molecular; D005947:Glucose / Q000494:pharmacology; D007328:Insulin / Q000096:biosynthesis; D015640:Ion Channel Gating / Q000187:drug effects / Q000502:physiology; D007515:Islets of Langerhans / Q000737:chemistry*; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D009543:Nifedipine / Q000494:pharmacology; D018408:Patch-Clamp Techniques; D011188:Potassium / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D015183:Restriction Mapping; D013111:Spider Venoms / Q000494:pharmacology*; D015384:Zona Glomerulosa / Q000737:chemistry* / Q000166:cytology; D020867:omega-Agatoxin IVA
D002118:Calcium; D002121:Calcium Channel Blockers; D015220:Calcium Channels; D020864:Calcium Channels, N-Type; D005947:Glucose; D007328:Insulin; D009543:Nifedipine; D011188:Potassium; D013111:Spider Venoms; D020867:omega-Agatoxin IVA