MCU and ischemia: During ischemia, a decrease in pH can inhibit proteins or stimulate their downregulation (* p < 0.05), such as a 3.6-fold decrease in the Na+/Ca2+ exchanger NCX1 (Figure 7A) and a 2.9-fold reduction in mitochondrial Ca2+ uniporter MCU in the 6-month-old hearts (Figure 7B).