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Hepatic glycogen patterns are described for rats adapted to a precisely controlled feeding schedule and ad libitum fed rats. Liver samples were processed for biochemical and histochemical glycogen analysis at precise intervals following a 22 hour fast and a 2 hour meal. Histochemical determination of glycogen (PAS) after freeze substitution showed lobular patterns of hepatic glycogen which correlate with chemically determined glycogen levels and nutritional states of the rats. After 22 hour fasting, hepatocytes from rats with low glycogen levels (< 0.09% ) exhibited no significant staining. In control fed rats, feeding caused glycogen deposition throughout the lobule but in greatest concentration centrilobularly throughout the early phases of glycogen accumulation. As glycogen deposition continued, periportal lobular patterns were observed in rats with high glycogen levels (> 5% ). Glycogen depletion reduced glycogen staining in cells throughout the lobule, but centrilobular patterns prevailed until late in depletion when periportal patterns appeared. Ad libitum-fed rats showed similar glycogen patterns except maximum deposition was characterized by centrilobular or even lobular distribution of glycogen, and periportal patterns of glycogen were seen only rarely in extreme fasted rats. Differences in lobular patterns between ad libitum and control fed rats is apparently related to lower maximum hepatic glycogen levels reached by ad libitum-fed animals.The mammalian liver is important in regulating blood glucose by storing and breaking down hepatic glycogen after appropriate stimulation. Many biochemical details of glycogenolysis and glycogenesis have been reported and much work has been directed toward elucidating the control mechanisms of these processes. (Scrutton and Utter, '68; Robison et al., '68; Villar-Palasi and Larner, '70; Ryman and Whelan, '71). A problem of considerable importance for studies of glycogen metabolism at the cellular level is an accurate description of glycogen patterns in the liver during deposition and depletion of the carbohydrate.In general, investigators have agreed that hepatic intralobular differences in glycogen distribution exist during a cycle of feeding and fasting, but the precise pattern was unclear. Bock and Hoffman (1872) reported that liver glycogen in rabbits was deposited initially around the central vein and only later in more peripheral regions. This finding was confirmed in studies of livers from a variety of species AM. J. ANAT., 140: 299-338.by several workers (Noel, '23; Kater, '33; Forsgren, '35; Eger and Ottensmeir, '52; Themann, '63; Corrin and Aterman, '68). In contrast to this, others claimed that glycogen deposition proceeded from the periphery of the lobule to more centrally situated hepatocytes (Smith, '31; Kater, '33; Edlund and Holmgren, '40; Deane, '44; Ekman and Holmgren, '49).Literature on glycogen patterns during depletion also presents conflicting results. Noel ('23) reported that hepatic glycogen patterns during glycogenolysis were the reve...
Hepatic glycogen patterns are described for rats adapted to a precisely controlled feeding schedule and ad libitum fed rats. Liver samples were processed for biochemical and histochemical glycogen analysis at precise intervals following a 22 hour fast and a 2 hour meal. Histochemical determination of glycogen (PAS) after freeze substitution showed lobular patterns of hepatic glycogen which correlate with chemically determined glycogen levels and nutritional states of the rats. After 22 hour fasting, hepatocytes from rats with low glycogen levels (< 0.09% ) exhibited no significant staining. In control fed rats, feeding caused glycogen deposition throughout the lobule but in greatest concentration centrilobularly throughout the early phases of glycogen accumulation. As glycogen deposition continued, periportal lobular patterns were observed in rats with high glycogen levels (> 5% ). Glycogen depletion reduced glycogen staining in cells throughout the lobule, but centrilobular patterns prevailed until late in depletion when periportal patterns appeared. Ad libitum-fed rats showed similar glycogen patterns except maximum deposition was characterized by centrilobular or even lobular distribution of glycogen, and periportal patterns of glycogen were seen only rarely in extreme fasted rats. Differences in lobular patterns between ad libitum and control fed rats is apparently related to lower maximum hepatic glycogen levels reached by ad libitum-fed animals.The mammalian liver is important in regulating blood glucose by storing and breaking down hepatic glycogen after appropriate stimulation. Many biochemical details of glycogenolysis and glycogenesis have been reported and much work has been directed toward elucidating the control mechanisms of these processes. (Scrutton and Utter, '68; Robison et al., '68; Villar-Palasi and Larner, '70; Ryman and Whelan, '71). A problem of considerable importance for studies of glycogen metabolism at the cellular level is an accurate description of glycogen patterns in the liver during deposition and depletion of the carbohydrate.In general, investigators have agreed that hepatic intralobular differences in glycogen distribution exist during a cycle of feeding and fasting, but the precise pattern was unclear. Bock and Hoffman (1872) reported that liver glycogen in rabbits was deposited initially around the central vein and only later in more peripheral regions. This finding was confirmed in studies of livers from a variety of species AM. J. ANAT., 140: 299-338.by several workers (Noel, '23; Kater, '33; Forsgren, '35; Eger and Ottensmeir, '52; Themann, '63; Corrin and Aterman, '68). In contrast to this, others claimed that glycogen deposition proceeded from the periphery of the lobule to more centrally situated hepatocytes (Smith, '31; Kater, '33; Edlund and Holmgren, '40; Deane, '44; Ekman and Holmgren, '49).Literature on glycogen patterns during depletion also presents conflicting results. Noel ('23) reported that hepatic glycogen patterns during glycogenolysis were the reve...
The effect of diet composition on diurnal changes in glycogen zonation patterns in rat liver was investigated in individually-caged male Sprague-Dawley rats adapted to the 2 + 22 controlled feeding and lighting schedule and to diets containing 30% casein/55% carbohydrates, 60% casein/25% carbohydrates, or 9.0% casein (30 rats/dietary group). Three rats from each dietary group were killed at the following times relative to the onset of feeding (0 min):--60, --30, 0, 15, 30, 45, 60, 90, 120, and 180 min. Glycogen in cryostat sections from the median and right lateral lobes of the liver was fixed and stained by standard techniques. The optical density of glycogen at points along the path between the central and portal veins of a given lobule was determined, and lobular glycogen gradients of replicate animals were integrated to form a composite lobular glycogen distribution profile. In the period from--60 to 0 min, liver glycogen levels were similar for rats on any of the diets, and the glycogen concentration was similar in periportal (P), midlobular (M), and centrilobular (C) hepatocytes. During the 0- to 45-min period, diet-related glycogen depletion occurred (90 > 60 > 30% casein) by asymmetrical glycogen loss (P > M > C hepatocytes) from the liver lobules. Similar food intake curves occurred for all diets. During the 45- to 180-min period, asymmetrical glycogen accumulation began in lobular parenchymal cells (P > M > C hepatocytes), and rate of accumulation was related to dietary to dietary composition (30 > 60 > 90% casein). The differential responses of parenchymal cells within liver lobules to physiological stimuli resulted in glycogen distribution changes that were rapid and of large magnitude. Our results are consistent with the hypothesis that periportal and midlobular hepatocytes are more metabolically responsive and active than centrilobular hepatocytes
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