Fig. 2. Cx36 downregulation by glucose is reversible and occurs at the transcriptional level. (A) INS-1 cells preincubated for 24 hours at 2 mM, 10 mM and 20 mM glucose were further incubated at 10 mM glucose for 24 hours. Densitometric analysis of three independent northern blots revealed that Cx36 expression levels returned to control values after 8 hours. Mean (± s.e.m.) of three independent experiments. ^***, P<0.001; ^**, P<0.01. (B) After a 24 hour preincubation at 2 mM, 10 mM or 20 mM glucose, INS-1 cells were exposed to 5 µg ml^-1 actinomycin D for 1 hour, 2 hours, 3 hours or 5 hours. Quantitative assessment of Cx36 mRNA levels (northern blot) showed that glucose had no effect on the stability of the Cx36 transcript.