Renal clearance of absorbed intact GFP in the frog and rat intestine.

Intestine absorption of intact green fluorescent protein (GFP) and its following accumulation in the renal proximal tubule cells after its intragastric administration have been established by confocal microscopy in the rat and frog. Reabsorbed GFP was revealed in the endosomes and lysosomes of the proximal tubule cells by the methods of GFP photooxidation and immunofluorescent microscopy. The GFP intestine absorption rate and GFP accumulation in the kidney were significantly higher in the frog than in the rat. No specific fluorescence was revealed in the liver and colon cells after the GFP intragastric administration. The data obtained indicate the ability of the small intestine in the frog and rat to absorb intact proteins and an important role of the kidney in exogenous protein metabolism.