Ca(2+)-induced Ca2+ Release from Internal Stores in INS-1 Rat Insulinoma Cells.
10.4196/kjpp.2011.15.1.53
- Author:
Kyung Jin CHOI
1
;
Dong Su CHO
;
Ju Young KIM
;
Byung Joon KIM
;
Kyung Moo LEE
;
Shin Hye KIM
;
Dong Kwan KIM
;
Se Hoon KIM
;
Hyung Seo PARK
Author Information
1. Department of Physiology, College of Medicine, Konyang University, Daejeon 302-718, Korea. hspark@konyang.ac.kr
- Publication Type:Original Article
- Keywords:
INS-1;
Caffeine;
Ryanodine;
Calcium release;
CICR
- MeSH:
Animals;
Caffeine;
Calcium;
Carbachol;
Cytosol;
Indoles;
Insulin;
Insulinoma;
Rats;
Ruthenium Red;
Ryanodine;
Ryanodine Receptor Calcium Release Channel
- From:The Korean Journal of Physiology and Pharmacology
2011;15(1):53-59
- CountryRepublic of Korea
- Language:English
-
Abstract:
The secretion of insulin from pancreatic beta-cells is triggered by the influx of Ca2+ through voltage-dependent Ca2+ channels. The resulting elevation of intracellular calcium ([Ca2+]i) triggers additional Ca2+ release from internal stores. Less well understood are the mechanisms involved in Ca2+ mobilization from internal stores after activation of Ca2+ influx. The mobilization process is known as calcium-induced calcium release (CICR). In this study, our goal was to investigate the existence of and the role of caffeine-sensitive ryanodine receptors (RyRs) in a rat pancreatic beta-cell line, INS-1 cells. To measure cytosolic and stored Ca2+, respectively, cultured INS-1 cells were loaded with fura-2/AM or furaptra/AM. [Ca2+]i was repetitively increased by caffeine stimulation in normal Ca2+ buffer. However, peak [Ca2+]i was only observed after the first caffeine stimulation in Ca2+ free buffer and this increase was markedly blocked by ruthenium red, a RyR blocker. KCl-induced elevations in [Ca2+]i were reduced by pretreatment with ruthenium red, as well as by depletion of internal Ca2+ stores using cyclopiazonic acid (CPA) or caffeine. Caffeine-induced Ca2+ mobilization ceased after the internal stores were depleted by carbamylcholine (CCh) or CPA. In permeabilized INS-1 cells, Ca2+ release from internal stores was activated by caffeine, Ca2+, or ryanodine. Furthermore, ruthenium red completely blocked the CICR response in permeabilized cells. RyRs were widely distributed throughout the intracellular compartment of INS-1 cells. These results suggest that caffeine-sensitive RyRs exist and modulate the CICR response from internal stores in INS-1 pancreatic beta-cells.
