Effects of vitamin A deficiency on the levels and distribution of retinol-binding protein and marker enzymes in homogenates and Golgi-rich fractions of rat liver.
The levels of retinol-binding protein, prealbumin, and several 'marker' enzymes were determined in homogenates, crude subcellular fractions and isolated Golgi apparatus prepared from the livers of vitamin A-deficient and control rats. Vitamin A deficiency led to a marked increase (3.5-fold) in hepatic retinol-binding protein concentration and to slight increases in hepatic pre-albumin levels, without affecting the levels of a number of marker enzymes localized in various subcellular compartments. The distributions of total protein and marker enzymes among various subcellular fractions were nearly identical in control and vitamin A-deficient preparations. In particular, vitamin A deficiency had no effect on the yield or enzymatic composition of isolated Golgi-rich fractions. In vitamin A-deficient rats, where the normal secretion of retinol-binding protein was blocked, a maximum of less than 10% of the total liver retinol-binding protein was accounted for in the Golgi. In contrast, in control rats, where the secretion of retinol-binding protein was proceeding at the normal rate, the relative amount of retinol-binding protein in Golgi increased to about 23% of the total liver pool. The data suggest that the Golgi apparatus is involved in the pathway of retinol-binding protein secretion from the liver, but demonstrate that the Golgi is not the major subcellular locus for retinol-binding protein in either normal or vitamin A-deficient rats.
D000818:Animals; D002458:Cell Fractionation; D006056:Golgi Apparatus / Q000378:metabolism*; D008099:Liver / Q000201:enzymology / Q000378:metabolism* / Q000473:pathology; D008297:Male; D009929:Organ Size; D011228:Prealbumin / Q000378:metabolism; D051381:Rats; D012177:Retinol-Binding Proteins / Q000378:metabolism*; D013347:Subcellular Fractions / Q000378:metabolism; D014018:Tissue Distribution; D014802:Vitamin A Deficiency / Q000378:metabolism*
D011228:Prealbumin; D012177:Retinol-Binding Proteins