This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Physiology
C natriuretic peptide is found in: 
Select and explain. 
A. Brain, B. Kidney, C. Pituitary, D. All of the above
D: All of the above
Answer: D: All of the above 
Explanation: A third member of this family has been named C-type natriuretic peptide (CNP) because it was the third in the sequence to be isolated. It contains 22 amino acid residues, and there is also a larger 53-amino-acid form. CNP is present in the brain, the pituitary, the kidneys, and vascular endothelial cells. However, very little is present in the hea and the circulation, and it appears to be primarily a paracrine mediator. Ref: Ganong's Review of Medical Physiology 23rd edition, Chapter 39.