Xylazine and ketamine-induced glycosuria in white-tailed deer

This study documents glycosuria effects of xylazine and ketamine in eight captive and 19 free-ranging white-tailed deer (Odocoileus virginianus) from January to April 1985. Mean urinary glucose:creatinine ratios in two groups of deer fed high protein-high energy and low protein-low energy diets and in free-ranging deer were 1,000, 719, and 259, respectively. Glucose did not occur in urine of deer immobilized by physical restraint. Glucose:creatinine increased with the time interval between xylazine injection and urine collection in the two groups of captive deer.     

Cholesterol catabolism in the rabbit in fasted and fed states.

Urinary and fecal endogenous steroid excretion of fed or fasted New Zealand white rabbits was determined by the isotopic steady state method after subcutaneous implantation of radioactive cholesterol. While plasma cholesterol was increasing during a 9-day fast, fecal steroid excretion decreased to 10% of the excretion rates in the fed state. Refeeding the fasted rabbits led to a decrease in plasma cholesterol and an increase in fecal endogenous steroid excretion. Urinary steroid excretion, which represented 18% of total endogenous steroid excretion for fed animals, decreased during fasting and increased during refeeding, but these changes were relatively small. The small intestine, cecum, and colon of fed or fasted rabbits had similar endogenous steroid was acidic steroid. During attempts to alter the circulating bile acid concentration by supplying deoxycholate (200 mg/day) to fed rabbits or cholestyramine (2 g/day) to fasted rabbits, plasma cholesterol concentration did not change to the same extent as during fasting or refeeding, respectively. The decreased cholesterol catabolism and the hypercholesterolemia that are seen in the fasting rabbit may result from decreased clearance of plasma cholesterol.     

Blood and urinary profiles of free-ranging desert mule deer in Arizona

As a corollary to a more comprehensive study on their ecology, we documented blood and urinary profiles for 10 free-ranging desert mule deer (Odocoileus hemionus crooki) (five males, five females) captured by net-gun shot from a helicopter during February 1988 in Saguaro National Monument, Arizona. Pursuit with the helicopter for netting deer ranged from 3 to 15 min. Blood profiles included seven hematological characteristics and 12 serum chemistries, electrolytes, hormones and enzymes. Urine samples were assayed for urea nitrogen, creatinine, sodium, potassium, calcium and phosphorus. Urinary data were compared as ratios to creatinine. Serum cholesterol was greater (P less than 0.05) in males than females. Pursuit time was correlated with serum non-esterified fatty acids (r = 0.67, P less than 0.05) and influenced urinary specific gravity (r2 = 0.77, P less than 0.004), urea nitrogen: creatinine (r2 = 0.79, P less than 0.005), and potassium: creatinine (r2 = 0.42, P = 0.08) ratios. Increasing specific gravity was related to urinary creatinine concentration (r2 = 0.72, P less than 0.008). All deer exhibited acute adrenal stimulation, accompanied by elevated serum creatine phosphokinase and urinary potassium: creatinine ratios, which were indicative of acute excitement and muscle trauma associated with the capture process. We demonstrated that urinary data are a valuable supplement to serum data in demonstrating effects of intense physical exertion, and both forms of data emphasize the need to assess capture-related excitability as a source of variation in blood and urine characteristics of free-ranging desert mule deer.     

Effect of fasting on body composition and responses to stress in sunshine bass

The integrated responses of the hormonal regulation of growth and stress in sunshine bass (Morone chrysops X Morone saxatilis) as regulated by feed deprivation were investigated. Groups of fish were fed 1.5% of the body weight per day or offered no feed for 4 weeks. Another group of fish was not fed for 3 weeks and feed was offered during the fourth week. Fish in each group were sampled immediately before or after a 15-min low water confinement stressor after each week of the experiment. Liver mass and liver glycogen content were decreased after one week of fasting and remained low until the end of the study. However, both recovered after a week of refeeding. Intraperitoneal fat was significantly lower after two weeks of fasting and did not recover after a week of refeeding. None of these components were affected by confinement stress. Plasma glucose in unstressed fish was generally unaffected by fasting or refeeding; however, plasma glucose increased after confinement stress in fed but not in fasted fish. The cortisol stress response was unaltered by fasting and remained robust. Plasma IGF-I generally decreased in fasted fish but was not significantly lower than fed fish until the fourth week. A week of refeeding did not restore plasma IGF-I concentrations. Plasma IGF-I concentrations were higher in confinement stressed fed fish after two and four weeks but were unchanged in the fourth week. There was no change in the plasma IGF-I concentrations in fasted or refed fish due to the stress. Liver weight and liver glycogen were essentially depleted after 2 weeks of fasting. The reduction of liver glycogen greatly reduced the glucose response to stress; however, the cortisol stress response was maintained for at least four weeks of fasting. Intraperitoneal fat was decreased very little after 4 weeks of fasting. Plasma IGF-I concentrations were reduced only after 3 weeks of fasting.     

Mitochondrial and peroxisomal oxidation of arachidonic and eicosapentaenoic acid studied in isolated liver cells

The partitioning between peroxisomal and mitochondrial beta-oxidation of [1-14C]eicosapentaenoic acid (20:5(n-3] and [1-14C]arachidonic acid (20:4(n-6)) was studied. In hepatocytes from fasted rats approximately 70% of the fatty acid substrate was oxidized with oleic, linoleic, eicosapentaenoic and docosahexaenoic (22:6(n-3)) acid, even more with adrenic (22:4(n-6)) and less with arachidonic acid. When the mitochondrial oxidation was suppressed by fructose refeeding and by (+)-decanoylcarnitine, the fatty acid oxidation in per cent of that in cells from fasted rats was with 18:1(n-9) 7%, 18:2(n-6) 8%, 20:4(n-6) 12%, 20:5(n-3) 20%, 22:4(n-6) 57% and for 22:6(n-3) 29%. The fraction of 14C recovered in palmitate and other newly synthesized fatty acids after fructose refeeding decreased in the order 22:4(n-6) greater than 22:6(n-3) greater than 20:5(n-3) greater than 20:4(n-6) and was very small with 18:1(n-9) and 18:2(n-6). In cells from both fed and fructose-refed animals 20:5(n-3) was efficiently elongated to 22:5(n-3) and 22:6(n-3). 20:5(n-3) and 20:4(n-6) were not elongated after fasting. The phospholipid incorporation with [1-14C]20:5(n-3) decreased during prolonged incubations while it remained stable with [1-14C]arachidonic acid. The results suggest that peroxisomes contribute more to the oxidation of 20:5(n-3) than with 20:4(n-6) although both substrates are probably oxidized mainly in the mitochondria.     

Nutrition and fetal brain maturation : II. Impact of maternal starvation on changing levels of acetylcholinesterase and enolase in vitro

The impact of maternal starvation during Days 17-20 of gestation was examined in 20-day fetal rat brain tissue cultured for 6 days in MEM and 10% adult rat serum. Acetylcholinesterase (AChE) activities were consistently greater in fetal brain cell cultures from starved mothers. When fetal tissues from starved mothers were continuously exposed to 72-h fasted serum, AChE activities increased from 1.03 +/- 0.14 to 1.59 +/- 0.21 mumol/h/mg protein (P less than 0.001). In fetal tissues from fed mothers, lower AChE activities were increased from 0.78 +/- 0.09 to 1.04 +/- 0.07 mumol/h/mg protein (P less than 0.05) when 72-h fasted serum was used to replace the fed serum during incubation. When fetal brain cell cultures from fed mothers were exposed for 6 days to graded concentrations of fed serum (2.5-15%), the activities of AChE fell reciprocally from 1.34 +/- 0.10 to 0.82 +/- 0.12 mumol/h/mg protein (P less than 0.05). The levels of AChE activity in tissues exposed to fasted serum were consistently greater, but fell similarly from 1.62 +/- 0.10 to 0.97 +/- 14 mumol/h/mg protein (P less than 0.01), when serum concentrations were increased from 2.5 to 15%. AChE activities were 30% higher in tissues incubated with cycloheximide 10(-3) M (P less than 0.02). Unlike AChE, fetal brain enolase activities were unaffected by maternal starvation. In fetal brain cell cultures from fed mothers, enolase fell from 1.85 +/- 0.10 to 1.37 +/- 0.12 mumol/min/mg protein following exposure to fasted instead of fed serum (P less than 0.02). In fetal cultures from starved mothers, enolase activities were depressed similarly from 1.76 +/- 0.08 to 1.41 +/- 0.09 mumol/min/mg protein when fasted replaced fed serum (P less than 0.02). Thus, the fetal brain cell cultures appear to maintain enzymatic realignments imposed by maternal starvation for at least 6 days. In addition, serum from fasted animals has significant growth inhibiting properties manifested by heightened activities of AChE and lower activities of enolase.     

Hematological and Blood Biochemical Effects of Fasting and Subsequent Oral Administration of Endotoxin in Prepubertal Gilts

The main objective of the present study was to investigate the effects of short-term fasting in gilts on endocrinological and blood biochemical parameters and, further, the effects of subsequent oral endotoxin (ET) administration. Group 1 was fasted for 30 h and then received feed with ET added. Group 2 was fasted for 30 h but received standard feed at refeeding. In group 3, gilts were fed every 6 h for 30 h. The major effects of fasting were: gradually increased concentration of plasma prostaglandin F2α metabolite, serum total bilirubin, serum free fatty acids, and decreased serum glucose. The values were normalized within 1–4 h of refeeding. Twelve hours after refeeding, the ET-refed gilts showed higher levels of serum total bile acids and polymorphonuclear leukocytes than those in group 2. It is possible that the observed changes during fasting reflect either an increased intestinal uptake of naturally present endotoxin or a reduced endotoxin detoxifying capacity of the liver. The increased bile acid concentration and polymorphonuclear leukocyte count following refeeding with ET-feed may indicate that orally administered ET is to some extent absorbed from the gut.     

Vitamin A status and its metabolism contribute to the regulation of hepatic genes during the cycle of fasting and refeeding in rats

Vitamin A (VA) status and its metabolism affect hepatic metabolic homeostasis. We investigated if VA status and metabolism contribute to energy metabolism and expression of hepatic genes in the cycle of fasting and refeeding. Zucker lean rats with VA sufficient (VAS) or VA deficient (VAD) status were respectively grouped as: ad libitum (VAS-AD or VAD-AD), 48-h fasted (VAS-Fasted or VAD-Fasted), 48-h fasted and refed a VAS diet (VAS-Refed-VAS or VAD-Refed-VAS), or refed a VAD diet (VAS-Refed-VAD or VAD-Refed-VAD) for 6 h. Respiratory exchange ratio (RER) of rats fed the VAS or VAD diet was monitored for 6 weeks. From week four, rats fed the VAS diet had higher RER than those fed the VAD diet. VAS-Refed rats had higher plasma levels of glucose, triglyceride, insulin and leptin than VAD-Refed rats. The mRNA and protein levels of hepatic genes for fuel metabolism in the fasting and refeeding cycle were determined using real-time polymerase chain reaction and immunoblot, respectively. The mRNA levels of glucokinase (Gck), sterol regulatory element-binding protein 1c (Srebp-1c), and fatty acid synthase (Fas) were lowered in VAS-Fasted and VAD-Fasted rats, and increased in VAS-Refed-VAS, VAS-Refed-VAD and VAD-Refed-VAS, but not VAD-Refed-VAD, rats. The ACL and FAS protein levels only dropped in VAS-Fasted rats and increased in VAS-Refed-VAS rats. The GK protein level decreased only in VAS-Fasted rats, and increased in VAS-Refed-VAS, VAS-Refed-VAD and VAD-Refed-VAS (but not VAD-Refed-VAD) rats. We conclude that VA status and its metabolism in the fasting and refeeding cycle contribute to the regulation of hepatic gene expression in rats.     

Fasting and refeeding cause rapid changes in intestinal tissue mass and digestive enzyme capacities of Atlantic salmon (Salmo salar L.)

Fasting and refeeding effects on gastrointestinal morphology and digestive enzyme activities of Atlantic salmon, held in tanks of seawater at 9 degrees C and 31 per thousand salinity, were addressed in two trials. Trial 1: Fish (mean body mass 1190 g) were fasted for 40 days and intestines sampled at day 0, 2, 4, 11, 19 and 40. Trial 2: Fish (1334 g), fasted for 50 days, were refed and sampled at day 0, 3 and 7. Mass, length, protein, and maltase, lactase, and leucine aminopeptidase (LAP) activities were analyzed for stomach (ST), pyloric caeca (PC), proximal (PI), mid (MI), and distal intestine (DI). PC contributed 50% of gastrointestinal mass and 75% of enzyme capacity. Fasting decreased mass and enzyme capacities by 20-50% within two days, and 40-75% after 40 days. In PC, specific brush border membrane (BBM) maltase activity decreased whereas BBM LAP increased during fasting. Upon refeeding, enzyme capacities were mostly regenerated after one week. The results suggest that refeeding should start slowly with about 25% of estimated feed requirement during the first 3 days, but may then be stepped up rapidly. Investigations of digestive processes of fed fish should only be performed when intestines are feed-filled to avoid bias due to effects of fasting.     

Effect of host feeding and available glucose on glycogen synthase and phosphorylase activities in Hymenolepis diminuta and Vampirolepis microstoma

The influences of host feeding and the availability of glucose in vitro on the activities of glycogen synthase and glycogen phosphorylase in Hymenolepis diminuta and in Vampirolepis microstoma were studied. The worms were recovered from hosts that had been fed ad libitum, starved for 24 hr, or starved 24 hr and then refed for 1 hr immediately prior to worm recovery. The ratios of active to inactive glycogen synthase and phosphorylase were correlated with the host feeding regimen prior to recovery. Glycogen synthase in H. diminuta was predominately in the inactive D form in worms from both fed and fasted hosts. One hour after refeeding, up to 80% of the synthase was in the active I form. Phosphorylase in H. diminuta was predominantly in the active a form in worms from fed and fasted hosts, but activity of this enzyme was suppressed in worms from refed hosts. When H. diminuta from fasted hosts was incubated in a balanced salt solution containing 40 mM glucose, glycogen synthase I increased, and phosphorylase a decreased. Glycogen synthase in V. microstoma was predominantly in the inactive D form in worms from both the fed and fasted hosts, but the proportion in the active I form increased to over half the total synthase by 1 hr of host refeeding. The proportion of glycogen phosphorylase a was high in worms from fed hosts and decreased, but not dramatically, in worms from fasted hosts. The results suggested that the worms had access to another source of glucose, probably from the host bile, and we measured a low but significant concentration of carbohydrate in the gall bladder bile of mice.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of age on fasting-induced changes in insulin, glucose, urea nitrogen, and free fatty acids in sera of sheep

The hypothesis that prepubertal ewe lambs are metabolically different from postpubertal ewes was tested. Ovariectomized ewes (4 years of age; n = 4) and lambs (6 months of age; n = 4) were fasted for 72 hr. Serum concentrations of insulin, glucose, urea nitrogen, and free fatty acids (FFA) were measured in blood samples taken at 6-hr intervals between 30 hr before and 72 hr after feed removal. Serum concentrations of urea nitrogen and glucose were not different (P greater than 0.20) between age groups before fasting. Serum concentrations of insulin in ewes increased toward the end of the prefast period whereas those in lambs did not (age x time, P less than 0.01). Serum concentrations of FFA in ewes tended to be lower (P less than 0.07) than those in lambs prior to fasting. During fasting, concentrations of insulin decreased (P less than 0.02) over time in ewes and lambs and did so in a similar manner (age x time, P greater than 0.70). Urea nitrogen increased (P less than 0.0001) in both fasted ewes and fasted lambs in a comparable manner (age x time, P greater than 0.20). Concentrations of glucose during fasting were not significantly affected (P greater than 0.90) by age. There was a tendency (P = 0.08) for concentrations of glucose to change over time but the pattern did not appear to be related to fasting. During fasting, concentrations of FFA tended to be higher (P less than 0.07) in lambs than in ewes and increased (P less than 0.0001) in both groups in a similar fashion (age x time, P greater than 0.10). The findings herein suggest that turnover of FFA in lambs may be slightly greater than that in ewes during the fed and fasted states.     

Effects of starvation and refeeding on elastase-induced emphysema

Adult rats received pancreatic elastase (75 U/100 g) intratracheally and were divided into three groups: fed, starved, and refed. Starved rats received one-third of their measured daily food consumption until they lost 40% body weight. The refed group was fed after 40% weight loss. A control group received saline intratracheally. Saline volume-pressure curve was shifted more significantly to the left of the control group in starved than in fed rats and was superimposed in refed and fed groups. Mean linear intercept was larger and alveolar surface area was smaller in starved than in fed rats compared with the control group; both were similar in fed and refed rats. Protein and hydroxyproline content of the lung were higher in fed than in control and in starved groups; after refeeding these returned to the control values. We conclude that starvation aggravates elastase-induced injury and that refeeding results in the complete recovery of the mechanical but only partial recovery of the morphometric changes induced by starvation.     

Secretion of lipoprotein lipid and synthesis of fatty acids, cholesterol and triacylglycerol by hepatocytes of fasted-refed rats

Synthetic rates of fatty acid, cholesterol and triacylglycerols, and contents and secretion of lipoprotein lipids, were determined in hepatocytes of rats fed ad libitum a fat-containing stock diet or of rats fasted for 48 h and then refed for 24 or 48 h with stock diet or with a glucose-rich fat-free diet. When compared with the values for the ad libitum-fed rats, fatty acid synthesis was lower in fasted rats, slightly increased in rats refed with the stock diet, but several-fold elevated after refeeding the glucose-rich fat-free diet. Cholesterol synthesis was decreased in the fasted cells, and restored to the control level upon refeeding either diet. Triacylglycerol synthesis from exogenous oleate was greatly stimulated in the cells of fasted-refed rats above the rate in cells of the ad libitum-fed rats, the increase being considerably higher after refeeding the glucose-rich fat-free diet than the stock diet. The amount of triacylglycerol secreted by the cells was also elevated by the fasting-refeeding treatment, but the difference between the two diets was much less pronounced than seen for the lipids' synthetic rates. This imbalance may underlie the huge accumulation of this lipid observed in the heptatocytes after refeeding the rats for 48 h with the glucose-rich fat-free diet.     

Glucose metabolism in proliferating epithelial cells from the rat colon.

1. The effects of fasting and fasting followed by refeeding on the activities of the oxidative pentose pathway (OPP) and the tricarboxylic acid cycle (TCA) in isolated rat colonocytes were estimated by the rate of production of 14CO2 from [1-14C]glucose and [6-14C]glucose, respectively. 2. Refeeding after a fast induced a 2-3-fold increase in glucose flux through the OPP and TCA cycle and the degree of change was similar in colonocytes from the proximal and distal colon. 3. Butyrate at a concentration of 40 mM inhibited the OPP by 20-30% (P less than 0.05) but had no effect on the activity of the TCA cycle. Glutamine at a concentration of 2 mM decreased the glucose flux through both the OPP and the TCA cycle by 30-50% (P less than 0.05). 4. Production of 14CO2 from the oxidation of butyrate or glucose indicated that the former was 5-7 times more active in colonocytes from fasted rats. After refeeding, however, butyrate utilization was similar to fasting values in the proximal colon but significantly lower (P less than 0.05) in the distal colon.     

The effect of intestinal anaphylaxis on postprandial motility in the rat

We have previously utilized a rat animal model to demonstrate that challenge of fasted sensitized animals with antigenic food protein is associated with diarrhea and altered intestinal myoelectric and motor activities. In this paper we examine the effect of intestinal anaphylaxis on postprandial motility in the same animal model. Hooded Lister rats were sensitized (S) by intraperitoneal injection of 10 micrograms egg albumin (i.e., antigen (Ag) and compared with sham-sensitized controls (C). Seven days later, three bipolar jejunal electrodes and a jejunostomy tube, for motility recording and Ag administration, were implanted. On day 14, intestinal myoelectric and motor activities were measured in fed animals before and after intraluminal challenge with Ag (100 mg egg albumin/0.5 mL saline) or placebo (P; 0.5 mL saline). Specific immunoglobulin E serum titres were greater than or equal to 1:64 in S animals, while C animals showed no response. None of the C animals challenged with P or Ag and none of the S animals challenged with P defecated after challenge, but all the S animals challenged with Ag developed diarrhea (p less than 0.001). There was no disruption or alteration of the fed motility pattern in C animals challenged with P or Ag, or S animals challenged with P. In fed S animals challenged with Ag the fed motility pattern persisted, but there was a significant (p less than 0.05) increase in the number of high-amplitude aborally propagating clustered contractions, where the phasic contractile activity was superimposed on a sustained tonic elevation of intraluminal pressure lasting 5-10 s.(ABSTRACT TRUNCATED AT 250 WORDS)     

Demonstration of a quiescent period for feeding controls in the developing rat

Feeding behaviour of rats during development was assessed by weighing pups before and after a 4 h feeding session. During the first postnatal week, fasted pups gained significantly more weight than fed pups. This difference disappeared during the second week, but reappeared during the third week and persisted through the fourth week. In another series, pups were weighed at 2 and 4 h after beginning feeding. This showed that fasted pups aged 6 days compensate by suckling longer than fed pups. At 10 and 14 days of age there were no differences between fed and fasted pups at either 2 or 4 h, but from 16 days onward, fasted pups had eaten significantly more than fed pups at both times. A control experiment showed that the lack of compensation by fasted pups aged 10-14 days did not reflect lack of availability of milk. Video-analysis of suckling behaviour at ages 6, 10 and 15 days provided further evidence for lack of feeding controls during the second postnatal week: at 6 and 15 days fasted pups spent more time actively sucking than did fed pups. Whereas at 10 days, there were no differences between fed and fasted pups. It is concluded that feeding controls are present during the first postnatal week, become quiescent during the second week and reappear during the third week.     

Postprandial leg uptake of triglyceride is greater in women than in men

The postprandial excursion of plasma triglyceride (TG) concentration is greater in men than in women. In this study, the disposition of dietary fat was examined in lean healthy men and women (n = 8/group) in either the overnight-fasted or fed (4.5 h after breakfast) states. A [14C]oleate tracer was incorporated into a test meal, providing 30% of total daily energy requirements. After ingestion of the test meal, measures of arteriovenous differences in TG and 14C across the leg were combined with needle biopsies of skeletal muscle and adipose tissue and respiratory gas collections to define the role of skeletal muscle in the clearance of dietary fat. The postprandial plasma TG and 14C tracer excursions were lower (P = 0.04) in women than in men in the overnight-fasted and fed states. Women, however, had significantly greater limb uptake of total TG compared with men on both the fasted (3,849 +/- 846 vs. 528 +/- 221 total micro mol over 6 h) and fed (4,847 +/- 979 vs. 1,571 +/- 334 total micromol over 6 h) days. This was also true for meal-derived 14C lipid uptake. 14C content of skeletal muscle tissue (micro Ci/g tissue) was significantly greater in women than in men 6 h after ingestion of the test meal. In contrast, 14C content of adipose tissue was not significantly different between men and women at 6 h. The main effect of nutritional state, fed vs. fasted, was to increase the postmeal glucose (P = 0.01) excursion (increase from baseline) and decrease the postmeal TG excursion (P = 0.02). These results support the notion that enhanced skeletal muscle clearance of lipoprotein TG in women contributes to their reduced postprandial TG excursion. Questions remain as to the mechanisms causing these sex-based differences in skeletal muscle TG uptake and metabolism. Furthermore, nutritional state can significantly impact postprandial metabolism in both men and women.     

Effect of a commercial trout diet on liver ultrastructure of fed and fasted yearling coho salmon, Oncorhynchus kisutch Walbaum

Yearling coho salmon were fed either a commercial trout (TC) diet or a diet consisting of homogenized adult Pacific Ocean coho salmon (PS), supplemented with vitamins and minerals. The hepatosomatic index of the TC-fed fish killed 12 h after the last feed or after 4 or 8 weeks of fasting were significantly larger ( P 0.05) than comparable PS-fed groups.
'Light' and'dark' hepatocyte cell types were evident in all groups although the dark cells were less numerous in the fasted fish. Hepatocytes of fasted fish contained markedly more endoplasmic reticulum than fed fish. Hepatocytic glycogen content of the TC-fed fish was higher than in PS-fed fish. Whereas in the TC-fed group hepatic glycogen was still evident in fish fasted for 8 weeks, the hepatocytes of the fasted PS-fed group contained little or no glycogen. The suitability of commercial fish diets for salmonids is discussed.     

Inactivation of liver aldolase in fasting rabbits: Evidence for the accumulation of two different immunoreactive forms

During prolonged starvation the activity of aldolase in crude rabbit liver extracts decreases to less than one-half the value observed in extracts of livers from fed animals. The specific activity of the enzyme purified by adsorption on phosphocellulose and elution with substrate is also approximately one-half that of the purified native enzyme. Both the level of enzyme activity and the specific activity are restored to normal within 36 h of refeeding. After removal of active aldolase from the liver extracts by adsorption on phosphocellulose an additional immunoreactive protein can be isolated by adsorption on antialdolase-Sepharose and elution with 4 m MgCl₂. This protein is devoid of catalytic activity and in livers of fasted rabbits accounts for nearly 40% of the total immunoreactive material. It has also been detected in extracts prepared from livers of fed rabbits, where it accounts for 10–20% of the total protein adsorbed by antialdolase-Sepharose. The low-activity enzyme isolated from livers of fasted rabbits cannot be reactivated by sulfhydryl compounds; it shows similar sensitivity to heat and denaturing agents as the enzyme isolated from livers of fed rabbits. The activity ratios with fructose 1,6-bisphosphate, fructose 1-phosphate, and triose phosphate are similar to those observed for the native liver enzyme.