Endogenous peptide activator of intestinal guanylyl cyclase; secreted mainly by the gastrointestinal mucosa. Regulates water and electrolyte transport in intestinal and renal epithelia.

6PPD-Q (6PPD-Quinone), a contaminant present in the environment and soil, is a derivative of the tire antioxidant N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (6PPD), which impairs the quality of spermatozoa in mice and induces impaired male fertility.

Vitamin K has blood coagulation action and is important for coagulation factors, matrix-Gla protein, and osteocalcin.