Fig. 3.

Cholesterol depletion attenuates CCh-evoked Ca²⁺ signals without affecting their potentiation by β-adrenoceptors. (A,B) Typical responses from a single HEK 293 cell with (B) or without (A) treatment with βMCD (at 20°C) and then stimulated in Ca²⁺-free HBS with CCh (1 mM), then isoproterenol (1 µM) and finally with ionomycin (Iono, 1 µM) to release any Ca²⁺ remaining within the intracellular stores. (C,D) Summary of results shows the percentage of cells responding to CCh alone, or to CCh with isoproterenol (C), and the amplitude of the peak increase in [Ca²⁺]_i evoked by each stimulus (D) for control and βMCD-treated cells. Results are means ± s.e.m. from n≥3 coverslips, with >50 cells analyzed from each. *P<0.05. (E) Populations of HEK-PR1 cells were stimulated with the indicated concentrations of CCh alone or with 8-Br-cAMP (10 mM, 20 minutes) with or without βMCD treatment (at 20°C). Results are means ± s.e.m. from three experiments. (F) Depletion of cholesterol selectively inhibits Ca²⁺ release evoked by CCh alone without affecting Ca²⁺ release by CCh with PTH (or isoproterenol).