ADCYAP1R1 and digestive system neoplasm: The significance of PAC1R-mediated signalling in maintaining normal pulmonary vascular tone during early postnatal life was demonstrated by Otto et al. In the advanced stages, corticosterone, triglyceride, free fatty acid, ketone body, and lactate levels were notably elevated in the serum of the PAC1R-null mice, accompanied by the onset of fatty liver and fatty degeneration in cardiac muscle cells.