<prompt> Renin is synthesized as a large preprohormone. It is secreted by:PCTDCTCollecting ductJuxtaglomerular apparatus  <response>: Active renin is formed in the secretory granules of the granular cells in the juxtaglomerular apparatus. Active renin has a half-life in the circulation of 80 min or less. Its only known function is to cleave the decapeptide angiotensin I from the amino terminal end of angiotensinogen renin substrate. Ref: Barrett K.E., Barman S.M., Boitano S., Brooks H.L. 2012. Chapter 38. Regulation of Extracellular Fluid Composition Volume. In K.E. Barrett, S.M. Barman, S. Boitano, H.L. Brooks Eds, Ganongs Review of Medical Physiology, 24e. 