Fig. 4. AMPK subunit isoforms and their phosphorylation in response to treatment of Clone 9 cells with sodium azide, AICAR and hypertonic sorbitol. Confluent dishes of cells were untreated (basal), exposed to 5 mM sodium azide (azide), 500 µM AICAR (AICAR) or 0.4 M sorbitol (sorbitol) for 60 minutes. Western blots of cell lysates were probed with antibodies against the 1 subunit of AMPK (a), against the 2 subunit (b) or with an antibody specific for the Thr₁₇₂-phosphorylated forms of the 1 and 2 AMPK subunits (c). The mobilities of molecular mass markers are indicated on the right. Arrows denote the position of the 63 kDa AMPK subunits.