Q. Rabbit erythrocytes and lungs are very similar to those found in humans. As such, lung-perfusion experiments investigating the role of vasodilation in microvasculature. A researcher is investigating the role of ATP release caused by red blood cell shearing and plasticity when travelling through the microvasculature of rabbit lungs. When the cells are passed through the lung tissue, the researcher notices there is a lack of vasodilation including an interruption in the cAMP cascade. However, this interruption is rectified, and vasodilation occurs, when ATP is introduced along with the erythrocytes. What mechanism is lacking in the cells and thus pointing to a disease state?