Figure 5. The effects of prenatal caffeine on biophysical properties of BK_Ca channels on myocytes from mesenteric arteries (MA).

(A) Representative single BK_Ca channel records in inside-out patches (HP = + 40 mV) from the control (a) and caffeine (b) myocytes exposed to increasing [Ca²⁺]_i. (B) Voltage dependence of BK_Ca channels in [Ca²⁺]_i at 10⁻⁶ mol/L. The line was drawn according to the best fits with the Boltzmann equation. (C) The effect of prenatal caffeine on Ca²⁺ sensitivity of BK_Ca channels. The data points were fitted with the Hill equation to obtain the calcium concentration necessary to open half of the channels (K_d) and the Hill coefficient (η^H). (D) Summary of time constant for open and close state of BK_Ca channels ([Ca²⁺]_i = 10⁻⁶ mol/L, HP = + 40 mV; n = 30 cells, 7 animals/each group). (E–F) Representative single BK_Ca channel recording in inside-out patches (HP = + 40 mV, [Ca²⁺]_i = 10⁻⁷ mol/L) from the control (E) and caffeine (F) myocytes exposed to 10⁻⁶ mol/L tamoxifen (Tam). (G) Bar plot summarizes the mean ± SEM fold change in the Normalized NPo of BK_Ca channels after the application of Tam. (n = 30 cells, 7 animals/each group). (H–I) Protein expression of BK_Ca α (H) and β1-subunit (I). The α and β1-subunit expression in the caffeine MA was presented relative to control vessels (n = 6 each group). *P < 0.05, control vs. Caffeine. Gels were treated under the same experimental conditions with the control and experimental groups treated together.