Fig. 5.

Effects of oligomycin on stimulated chloride secretion (forskolin + IBMX) and AMPK activation in perfused shark rectal glands. All glands were perfused with elasmobranch Ringer’s bubbled with 99% O₂ and 1% CO_2. Baseline secretion levels were established for 30 min before the addition of forskolin (1 µM) and IBMX (100 µM). Stimulation with F + I was carried out for 45 min (A). Oligomycin (2 μM) was added at 45 min, and perfusion was continued to 75 min. Oligomycin treatment markedly inhibited chloride secretion. B: glands were snap frozen in liquid N₂, and rectal gland homogenates were immunoblotted with specific antibodies against AMPKα (tAMPK), pThr¹⁷²AMPKα (pAMPK), and GAPDH. C: immunoblots were quantified with densitometry and pAMPK/tAMPK ratios were normalized to F + I-perfused controls (n = 3, **P < 0.01, Student’s t-test).