ITPR1 and chronic obstructive pulmonary disease: In addition, we performed RT‐qPCR analysis to further determine the IP3R mRNA level in peripheral blood samples from patients with COPD (who had smoked for more than 15 years) and volunteer non‐smokers, which showed that the transcription of IP3R was also significantly reduced in the patients with COPD (P < .05, Figure 2B).