Ca(2+)-induced Ca2+ Release from Internal Stores in INS-1 Rat Insulinoma Cells

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.

Drinking Problems of Hepatitis B Virus Healthy Carriers in Korean Population

BACKGROUND: Heavy drinking may be a cause of serious health problems in hepatitis B virus carriers. The aim of this study was to reveal the degree of drinking problems in the Korean hepatitis B virus healthy carriers. METHODS: The subjects were 218 hepatitis B virus healthy carriers (124 males and 94 females) recruited from those who visited the Health Promotion Center of Chungnam National University Hospital for a general health check-up. Drinking problems of the subjects were evaluated by the AUDIT (Alcohol Use Disorders Identification Test) questionnaire. RESULTS: The AUDIT scores (mean+/-SD) of the male subjects (9.6+/-7.9) were significantly (P <0.001) higher than those of the female subjects (2.7+/-5.2). The individuals with heavy drinking (more than 14 drinks in males and 7 drinks in females per week) are 24 (19.4%) in males and 5 (5.3%) in females. Alcohol use disorders were suspected in 36 (29.0%) males and 4 (4.3%) females. CONCLUSION: It is suggested that, in Korea, clinical attention in primary health care should be focused on reducing the alcohol consumption among the hepatitis B virus carriers, considering a large proportion have drinking problems and the possible harmful effect on their health by heavy drinking.