Technical note: Extrapolation of hepatic glycogen concentration of the whole organ by performing a liver biopsy

摘要

Glycogen, a complex polysaccharide, is the form ofstorage of glucose in mammals that can be releasedrapidly when needed. Recent studies have mainlyreported hepatic glycogen concentration for earlylactatingcows, when the energy demand is higherthan the energy supply from dry matter intake, drivingthe cow to use the energy stored as hepatic glycogen.Generally, liver samples are obtained through percutaneousneedle biopsies in the right lobe of the liver.Our objective was to analyze the variation of glycogenconcentration in the livers of Holstein and Jersey cowsamong different liver locations representing all lobes,to evaluate whether samples obtained by liver biopsiesare representative of the whole organ. Liver from 10culled lactating cows (5 Holstein and 5 Jersey cows)from 30 to 113 mo of age at slaughter were obtained.Each liver was sampled no more than 3 h after deathon the following sites: 3 sites in the right lobe (1 to 3),2 in the diaphragmatic surface of the left lobe (4 and5), 3 in the visceral surface of the left lobe (6 to 8),1 in the quadrate lobe (9), and 1 in the caudate lobe(10). Samples were snap frozen in liquid N_2 and werethen analyzed for glucose concentration after conversionof glycogen to glucose using amyloglucosidase (EC3.2.1.3). Glycogen results are reported as grams of glucoseper 100 g of wet weight of liver (i.e., percent of wetweight of liver). Liver weights averaged 5.1 [standarddeviation (SD) 1.2, minimum 3.3, maximum 6.2] kg forHolstein and 6.0 (SD 1.8, minimum 4.7, maximum 8.9)kg for Jersey cows. Holstein cows [1.31, standard errorof the mean (SEM) 0.05% of wet weight] had greaterliver glycogen concentration than did Jersey cows (0.75,SEM 0.05% of wet weight). No significant differencewas noted among the 10 liver locations regarding glycogenconcentration and averaged, for both breeds, 1.03%of wet weight (SEM 0.10). These results suggest that,in dairy cows, percutaneous needle liver biopsy in theright lobe is an accurate technique to fairly extrapolateglycogen concentration of the whole organ.