ABSTRACT
Caffeine is an alkaloid which belongs to the family of methylxanthines and is present in beverages, food and drugs. Caffeine competitively antagonizes the adenosine receptors (AR), which are G protein-coupled receptors largely distributed throughout the body, including brain, heart, vessels and kidneys. Caffeine consumption has a well-known diuretic effect. The homeostasis of salt and water involves different segments of the nephron, in which adenosine plays complex roles depending on the differential expression of AR. Hence, caffeine increases glomerular filtration rate by opposing the vasoconstriction of renal afferent arteriole mediated by adenosine via type 1 AR during the tubuloglomerular feedback. Caffeine also inhibits Na(+) reabsorption at the level of renal proximal tubules. In addition, caffeine perturbs the hepatorenal reflex via sensory nerves in Mall's intrahepatic spaces. Here, we review the physiology of caffeine-induced natriuresis and diuresis, as well as the putative pathological implications.
