Imaging Ca2+ Signals in Small Pulmonary Veins at Physiological Intraluminal Pressures

Pulmonary veins (PVs) carry oxygen-rich blood from the lungs back to the left heart, thus serving an important function in the delivery of oxygen-rich blood to vital organs. However, most studies of pulmonary vasculature have focused on pulmonary arteries and capillaries under normal and disease conditions. Ca²⁺ signals are critical regulators of vascular function. Despite the critical physiological roles of PVs, Ca²⁺ signals in small intrapulmonary PVs have not been recorded under physiological conditions. Here, we describe a technique to record Ca²⁺ signal activity in mouse PVs isolated, cannulated and pressurized at 5 mmHg. By incorporating a Ca²⁺ indicator, we can study Ca²⁺ signals in the myocyte layer of small PVs using high-speed, spinning disk confocal imaging under physiological conditions. Our representative data indicates that the Ca²⁺ signals in small PV myocytes are mediated by openings of ryanodine receptor ion channels. This method will be of considerable interest to researchers in the field of pulmonary vascular physiology and disorders.