Circulating natriuretic peptide hormones act to maintain homeostasis with regard to blood volume, blood pressure, and salt balance. When the myo-endocardial cells of the atrium sense an increase in blood volume or pressure, they release A- or B-type atrial natriuretic peptides (ANPs). These peptides, acting through guanylate cyclase receptors, dilate blood vessels and stimulate salt excretion by inhibiting sodium chloride reabsorption in the collecting ducts of the kidney. As the salt concentration within the ducts increases osmotic pressure, diuresis occurs. C-type natriuretic peptide, produced in the hypothalamus and pituitary, causes dilation in the circulatory system, including the heart, but has little effect on the kidney. Urodilatin is a paracrine natriuretic peptide, produced in the proximal tubules of the kidney, and acting in the collecting ducts. We offer all of these peptides, from several vertebrate sources, as well as some active peptide fragments. Atriopeptin II, for example, relaxes smooth muscle both in veins and in the gut. Dendroaspis natriuretic peptide, originally isolated from green mamba snake venom, is structurally similar to the A-,B-, and C-ANP′s, and exerts the same physiological functions.

Researchers will also find here several peptide hormones with effects on appetite and energy metabolism. Pancreatic polypeptide and derivatives work through neuropeptide Y receptors. Pancreastatin, which is elevated in diabetes, and the catecholamine release inhibitor catestatin are peptide hormones resulting from the enzymatic cleavage of chromagranin.