Decreased hepatic retinyl palmitate hydrolase activity in protein-deficient rats.
28-day-old weanling rats were fed a diet containing 3% casein as the only source of protein for eight weeks to induce protein deficiency. When compared to control animals (fed a diet containing 25% casein), these rats had significantly lowered body (5.2-fold reduction) and liver (2.5-fold reduction) weights. The circulatory level of retinol (nmol per ml plasma) as well as retinol (nmol per g tissue) in the liver of these protein-deficient animals were also reduced significantly, although their liver concentration of retinyl palmitate (nmol per g tissue) was comparable to that of the control group. Assay of liver tissue for retinyl palmitate hydrolase activity revealed a 4-fold reduction (compared to that of control animals) of specific enzyme activity (nmol retinol formed per g protein per h). These findings suggest that severe protein deficiency results in a decreased hydrolysis of retinyl esters in the liver, which may be in part responsible for the reduced level of metabolically 'active' retinoids available for normal physiological functions.
D000818:Animals; D002265:Carboxylic Ester Hydrolases / Q000378:metabolism*; D004224:Diterpenes; D008099:Liver / Q000201:enzymology; D008297:Male; D011488:Protein Deficiency / Q000378:metabolism*; D051381:Rats; D000084562:Retinyl Esters; D014801:Vitamin A / Q000031:analogs & derivatives / Q000378:metabolism
D004224:Diterpenes; D000084562:Retinyl Esters; C022521:retinol-palmitate esterase; D014801:Vitamin A; C014794:retinol palmitate; D002265:Carboxylic Ester Hydrolases