Effect of Alloxan-diabetes on the Metabolism of Rabbit Colon Smooth Muscle

The metabolism of colon smooth muscle from normal and alloxan-diabetic rabbits was studied in vitro. Glucose uptake, incorporation of glucose-¹⁴C into glycogen and incorporation of leucine-¹⁴C into protein were determined. These three parameters were all depressed in diabetic smooth muscle incubated in a medium containing 5.6 mM glucose. Raising the glucose concentration in the medium to 22.2 mM almost doubled the glucose uptake both in diabetic and normal smooth muscle and at this glucose concentration no significant difference in this parameter was found. Insulin (0.1 U/ml) added in vim) stimulated glucose uptake, incorporation of glucose-¹⁴C into glycogen and incorporation of leucine-¹⁴C into protein in diabetic colon smooth muscle. Insulin stimulated glucose uptake to the same degree in normal and diabetic colon smooth muscle, while its effect on glucose-¹⁴C and Ieucine-¹⁴C incorporation tended to be somewhat more pronounced in diabetic colon muscle.     

Effect of insulin and glucose on the glucose consumption and glycogen synthesis by the rat diaphragm

Insulin activated both the uptake of glucose-C¹⁴ from the medium and its incorporation into glycogen by the incubated diaphragm: the percentage of glucose-C¹⁴ incorporated into glycogen increased with an increase in the dose of insulin. An increase in the concentration of glucose in the medium also caused this more rapid assimilation by the muscle tissue. However, significant stimulation of glycogen synthesis was observed only in the presence of a high (unphysiological) glucose concentration in the incubation fluid; the percentage of glucose-C¹⁴ incorporated into glycogen remained small and constant. It is postulated that the glucose-C¹⁴ found in the case of substrate control is the result of exchange of the glucose residues of glycogen with intracellular glucose.     

Incorporation of leucine into human skeletal muscle proteins.

The in vitro incorporation of labelled leucine into human skeletal muscle proteins was studied with the aim to elucidate the relationship between the amino acid tissue pools and protein biosynthesis. The distribution volumes of leucine and cycloleucine in skeletal muscle tissue were similar but the equilibration time was shorter for leucine than for cycloleucine. The cellular uptake of leucine and cycloleucine was competitively inhibited by increased concentration of amino acids in the medium indicating an active transport. Optimal stimulation for incorporation of leucine into proteins was obtained at an amino acid concentration in the medium corresponding to 10 times that of normal human plasma. The incorporation of 14C-leucine into skeletal muscle proteins was linear before the total pool of free intracellular 14C-leucine and the incorporation rate of leucine calculated from the specific activity in the medium versus the amino acid concentration in the medium were different in the same experiment indicating a re-utilization of amino acids released at protein degradation. The results are compatible with the hypothesis that the proteolytically released amino acids have a competitive advantage for incorporation as compared with extra- and intracellular free amino acids. It is concluded that the amino acid pool which is in the immediate continuity with the protein biosynthesis sites equilibrates rapidly with the extracellular amino acid pool.     

Effect of fasting and refeeding on glucose metabolism in rat aorta

The effect of refeeding on accumulation of [14C]glucose carbon, oxidation of [14C]glucose and glycogen concentration in rat aortic intima-media was studied in rats fasted for 3 days. Accumulation of glucose carbon and glucose oxidation were determined by incubating rat aorta in vitro for 2 h with 5.6 mM 14C-labelled glucose in the medium. Refeeding with standard pellets for 2-4 h augmented [14C]glucose accumulation in rat aorta but had no significant effect on glucose oxidation. The glycogen concentration in rat aorta tended to increase. After refeeding for 16 h both [14C]glucose incorporation and [14C]glucose oxidation were increased in rat aorta. Refeeding with carbohydrate-rich pellets (92% carbohydrate) for 3 h increased blood glucose more than did protein-rich (92% protein) pellets, whereas the rise in plasma insulin was about the same. The accumulation of [14C]glucose carbon measured during the subsequent in vitro incubation for 2 h was augmented after refeeding with protein-rich pellets and slightly reduced after carbohydrate-rich pellets. Refeeding of diabetic rats for 2 h with standard pellets increased plasma insulin and markedly increased blood glucose but had no effect on aortic [14C]glucose incorporation. Intravenous infusion of glucose in normal rats for 2 h markedly raised blood glucose but did not increase the aortic glucose incorporation. Raising the ambient glucose concentration from 5 to 10 mM during incubation of normal rat aorta in vitro for 2 h slightly decreased the [14C]glucose incorporation determined during a subsequent incubation for 2 h. These results suggest that refeeding with standard pellets augments glucose incorporation and glucose oxidation in rat aorta.(ABSTRACT TRUNCATED AT 250 WORDS)     

Incorporation of Leucine into Human Skeletal Muscle Proteins: A Study of Tissue Amino Acid Pools and their Role in Protein Biosynthesis

The in vitro incorporation of labelled leucine into human skeletal muscle proteins was studied with the aim to elucidate the relationship between the amino acid tissue pools and protein biosynthesis. The distribution volumes of leucine and cycloleucine in skeletal muscle tissue were similar but the equilibration time was shorter for leucine than for cycloleucine. The cellular uptake of leucine and cycloleucine was competitively inhibited by increased concentration of amino acids in the medium indicating an active transport. Optimal stimulation for incorporation of leucine into proteins was obtained at an amino acid concentration in the medium corresponding to 10 times that of normal human plasma. The incorporation of ¹⁴C-leucine into skeletal muscle proteins was linear before the total pool of free intracellular ¹⁴C-leucin had reached an equilibrium. The regression coefficients for the semilogarithmic plots of the labelling rate of proteins with ¹⁴C-leucine and the incorporation rate of leucine calculated from the specific activity in the medium versus the amino acid concentration in the medium were different in the same experiment indicating a re-utilization of amino acids released at protein degradation. The results are compatible with the hypothesis that the proteolytically released amino acids have a competitive advantage for incorporation as compared with extra- and intracellular free amino acids. It is concluded that the amino acid pool which is in the immediate continuity with the protein biosynthesis sites equilibrates rapidly with the extracellular amino acid pool.     

Quantitation of muscle glycogen synthesis in normal subjects and subjects with non-insulin-dependent diabetes by 13C nuclear magnetic resonance spectroscopy

To examine the extent to which the defect in insulin action in subjects with non-insulin-dependent diabetes mellitus (NIDDM) can be accounted for by impairment of muscle glycogen synthesis, we performed combined hyperglycemic-hyperinsulinemic clamp studies with [13C]glucose in five subjects with NIDDM and in six age- and weight-matched healthy subjects. The rate of incorporation of intravenously infused [1-13C]glucose into muscle glycogen was measured directly in the gastrocnemius muscle by means of a nuclear magnetic resonance (NMR) spectrometer with a 15.5-minute time resolution and a 13C surface coil. The steady-state plasma concentrations of insulin (approximately 400 pmol per liter) and glucose (approximately 10 mmol per liter) were similar in both study groups. The mean (+/- SE) rate of glycogen synthesis, as determined by 13C NMR, was 78 +/- 28 and 183 +/- 39 mumol-glucosyl units per kilogram of muscle tissue (wet weight) per minute in the diabetic and normal subjects, respectively (P less than 0.05). The mean glucose uptake was markedly reduced in the diabetic (30 +/- 4 mumol per kilogram per minute) as compared with the normal subjects (51 +/- 3 mumol per kilogram per minute; P less than 0.005). The mean rate of nonoxidative glucose metabolism was 22 +/- 4 mumol per kilogram per minute in the diabetic subjects and 42 +/- 4 mumol per kilogram per minute in the normal subjects (P less than 0.005). When these rates are extrapolated to apply to the whole body, the synthesis of muscle glycogen would account for most of the total-body glucose uptake and all of the nonoxidative glucose metabolism in both normal and diabetic subjects. We conclude that muscle glycogen synthesis is the principal pathway of glucose disposal in both normal and diabetic subjects and that defects in muscle glycogen synthesis have a dominant role in the insulin resistance that occurs in persons with NIDDM.     

Influence of Acetate on Glucose Metabolism in the Perfused Hind-Quarter of the Rat

The metabolism of U-¹⁴C-glucose and U-¹⁴C-acetate and the interaction between the two substrates in the perfused hind-quarter of the rat was studied. 5 % of glucose taken up was oxidized to CO., accounting for 15 % of total oxygen consumption. Glucose was mainly incorporated into glycogen, while incorporation into lipids was negligible. Acetate did not significantly alter glucose uptake, ¹⁴C-glucose oxidation or the incorporation of ¹⁴C-glucose into glycogen and lipids. 45% of acetate taken up was oxidized to CO₂ accounting for 20–25 % of total oxygen consumption. Insulin did not affect acetate uptake but increased %-acetate oxidation. Oxygen consumption was slightly increased by simultaneous oxidation of glucose and acetate and in this situation the tissue content of high-energy phosphate compounds was slightly elevated. It is concluded that only minor effects by acetate on glucose metabolism in the perfused skeletal muscle were found. The insignificant effects compared to previously reported studies on heart tissue (Neely and Morgan 1974) can be explained by differences in acetate metabolism between the two tissues.     

Serum from diabetic patients enhances synthesis of arterial basement membrane-like material in cultured smooth muscle cells

The effect of serum from both type I and type II diabetic subjects on the metabolism of arterial basement membrane (BM)-like material was studied in cultures of rabbit aortic smooth muscle cells. The basement membrane-like material was isolated from the cell-layer by a combined sonication and centrifugation technique. Serum from type I diabetic persons added to the incubation medium increased statistically significantly the incorporation of L-[4,5]-3H-leucine into the basement membrane-like material as compared to serum from non-diabetic subjects (2P less than 0.05). The same effect was seen with serum from type II diabetic patients as compared to serum from nondiabetic subjects (2P less than 0.05). No effect of serum from type I diabetic persons was seen in degradation experiments. Incubation medium supplemented with normal serum and extra glucose neither changed the production of basement membrane-like material nor the disappearance rate of radioactive leucine from the basement membrane-like material in degradation experiments. The present study indicates that serum from diabetic subjects enhances the production of arterial basement membrane-like material from arterial smooth muscle cells in culture. The obtained data may be relevant for the understanding of the development of macroangiopathy among diabetic patients.     

Regulation of chondrosarcoma metabolism by cyclic adenosine 3'5'-monophosphate

The in vitro effects of cyclic AMP on amino acid transport and synthesis of macromolecules in the Swarm rat chondrosarcoma were investigated using the cyclic AMP analogue, N6-monobutyryl cyclic AMP (MBcAMP), and the phosphodiesterase inhibitor, 3-isobutyl-1-methylxanthine (MIX). Amino acid transport was assessed by measuring alpha-amino-[1-14C]isobutyrate (AIB) uptake. The synthesis of macromolecules was estimated by measuring radiolabeled precursor incorporation into total proteins, proteoglycan, and RNA. MBcAMP stimulated [14C]AIB uptake, [3H]uridine transport, and UTP formation. MBcAMP inhibited 35SO4 and [3H]leucine incorporation into proteoglycan and stimulated [3H]uridine incorporation into RNA. MIX elevated endogenous cyclic AMP levels in the Swarm rat chondrosarcoma and mimicked the effects of MBcAMP on AIB transport and radiolabeled precursor incorporation into macromolecules. For comparative purposes, the effects of MBcAMP on AIB uptake and macromolecule synthesis in rat costal cartilage segments were investigated. MBcAMP and MIX stimulated AIB uptake by costal cartilage segments, inhibited [3H]leucine incorporation into total protein and 35SO4 incorporation into proteoglycan, and had no effect on [3H]uridine incorporation into RNA.     

Insulin action in pancreatic acini from streptozotocin-treated rats. I. Stimulation of protein synthesis

Pancreatic acini were prepared from rats rendered diabetic with streptozotocin. In this tissue, insulin stimulated [3H]leucine incorporation into protein. The full effects of insulin on this function were not immediate but increased linearly with time for up to 2 h of incubation. Insulin had a detectable effect on l eucine incorporation at 50 pM, a half-maximal effect at 0.7 nM, and a maximal effect at 30 nM. Desdipeptide proinsulin was only 10% as potent as native insulin in stimulating [3H]leucine incorporation, whereas proinsulin and desoctapeptide insulin were only 1% as potent. Insulin also increased the incorporation of [3H]valine and [35S]methionine into protein but did not increase the influx of either [14C]cycloleucine or alpha-[3H]aminoisobutyric acid. These observations suggested that the increased incorporation of labeled amino acid into protein reflected stimulation of protein synthesis rather than stimulation of amino acid transport. Furthermore, insulin at 1.67 nM significantly increased the acinar cell concentration of amylase. The present findings are consistent therefore with the concept that insulin regulates pancreatic exocrine functions, including protein and enzyme synthesis.     

The effects of insulin replacement and withdrawal on hepatic ultrastructure and biochemistry

This study examines the early hepatic biochemical and ultra-structural responses to insulin replacement in streptozotocin-diabetic rats and insulin withdrawal from insulin-maintained diabetic rats. Insulin administration rapidly lowered plasma glucose and the elevated glucose-6-phosphatase (G-6-Pase) specific activity of the diabetic rats. However, hepatic glycogen did not increase until after 3 hr of insulin treatment. Hepatic ultrastructure responded to insulin replacement after the decline in glucose and G-6-Pase. This was seen in periportal hepatocytes as a reduction in the close association between smooth endoplasmic reticulum (SER) and glycogen particles in the diabetic animals. The treated rats showed hepatic SER restricted to the periphery of glycogen masses, as is characteristic of these cells from normal rats, in many cells by 6 hr and all cells by 18 hr. Insulin withdrawal from insulin-treated diabetic rats elicited nearly a total reversal of the above events. Plasma insulin declined to a value half that of the normal rats by 6 hr after withdrawal; concurrently, plasma glucose rose sharply to hyperglycemic values as hepatic glycogen content dropped. Following the rise in plasma glucose and fall in glycogen content, G-6-Pase specific activity increased and by 16 hr reached the high values characteristic of the diabetic animal. Hepatic ultra-structure was also changed as evidenced by an intrusion of elements of the SER into the dense glycogen masses; the result was dispersed glycogen closely associated with SER as seen in the diabetic animal. It is concluded that the hepatic response to insulin replacement in diabetic animals and diabetic onset in insulin-withdrawn animals is rapid and occurs through defined stages.     

Insulin Antagonistic Effect of Human Plasma Albumin on Protein Synthesis in vitro and on Glycogen Synthesis in vivo in the Rat Diaphragm Muscle

The earlier finding of an antagonistic effect of human plasma albumin on the insulin-stimulated glucose uptake of the cut rat diaphragm in vitro has been confirmed. In the intact rat hemidiaphragm in vitro 1 mU of insulin per ml caused a marked increase (40–70 per cent) of the incorporation of ¹⁴C-labelled phenylalanine into protein. Adding 5 per cent albumin caused a significant reduction of this insulin effect. Intraperitoneal injection of 1mU of insulin caused a marked increase in glycogen content and ¹⁴C-labelled glucose incorporation into glycogen in the diaphragm muscle in vivo. This effect was antagonized by the simultaneous injection of 50–150 mg of “antagonistic” albumin; control injections of “non-antagonistic” albumin had no such effect. Increasing the insulin dose 10-fold abolished the antagonistic effect of the albumin. The result support the assumption that the “synalbumin” antagonist is a physiological antagonist of insulin action.     

Effect of insulin-like growth factor-I on metabolism in bovine mesenteric arteries

The effect of insulin-like growth factor-I (IGF-I) on glucose accumulation, amino acid uptake and incorporation of amino acid into protein was studied in arterial smooth muscle. Accumulation of [14C]glucose, uptake of [14C]alpha-aminoisobutyric acid (AIB) and incorporation of [14C]phenylalanine into protein were measured in intima-media preparations of bovine mesenteric arteries (BMA) incubated with IGF-I for 2, 4 or 6 h. IGF-I (2.2 nmol l-1) increased the accumulation of glucose into BMA after 4 h (P = 0.0079) and 6 h incubation (P = 0.0027) and in a concentration of 22 nmol l-1) also after 2 h (P = 0.015). The uptake of AIB and the incorporation of phenylalanine were increased after 4 h incubation with 2.2 nmol l-1) IGF-I (P = 0.0045 and P = 0.026, respectively). The effects of IGF-I on all of the metabolic parameters were dependent on incubation time and concentration of IGF-I. Concentration-effect curves were determined for the effect of IGF-I and also for insulin on glucose accumulation in BMA incubated for 6 h. The concentration-effect relationships for IGF-I and insulin were very similar with pD2 values of 7.6 +/- 0.2 (EC50 = 27 nmol l-1) and 7.5 +/- 0.2 (EC50 = 34 nmol l-1), respectively. No additive effect of IGF-I and insulin in supra-physiological concentrations (1.0 mumol l-1) could be demonstrated. These results show that IGF-I has metabolic effects which are similar to the effects of insulin in vascular smooth muscle and suggest that IGF-I may be of importance for the metabolism in vascular smooth muscle.     

Improved insulin‐stimulated glucose uptake and glycogen synthase activation in rat skeletal muscles after adrenaline infusion: role of glycogen content and PKB phosphorylation

Aim: Effects of in vivo adrenaline infusion on subsequent insulin‐stimulated glucose uptake and glycogen synthase activation was investigated in slow‐twitch (soleus) and fast‐twitch (epitrochlearis) muscles. Furthermore, role of glycogen content and Protein kinase B (PKB) phosphorylation for modulation insulin sensitivity was investigated. Methods: Male Wistar rats received adrenaline from osmotic mini pumps (≈150 μg kg^?1 h^?1) for 1 or 12 days before muscles were removed for in vitro studies. Results: Glucose uptake at physiological insulin concentration was elevated in both muscles after 1 and 12 days of adrenaline infusion. Insulin‐stimulated glycogen synthase activation was also improved in both muscles. This elevated insulin sensitivity occurred despite the muscles were exposed to hyperglycaemia in vivo. After 1 day of adrenaline infusion, glycogen content was reduced in both muscles; insulin‐stimulated PKB ser⁴⁷³ phosphorylation was increased in both muscles only at the highest insulin concentration. After 12 days of adrenaline infusion, glycogen remained low in epitrochlearis, but returned to normal level in soleus; insulin‐stimulated PKB phosphorylation was normal in both muscles. Conclusion: Insulin‐stimulated glucose uptake and glycogen synthase activation were increased after adrenaline infusion. Increased insulin‐stimulated glucose uptake and glycogen synthase activation after adrenaline infusion cannot be explained by a reduction in glycogen content or an increase in PKB phosphorylation. The mechanisms for the improved insulin sensitivity after adrenaline treatment deserve particular attention as they occur in conjunction with hyperglycaemia.     

Influence of altered O2 tension on substrate metabolism in perfused rat lung.

Effects of hypoxia (1.5 h) on glucose and palmitate metabolism were investigated in perfused lungs from normal rats and rats exposed for 24 h to hypobaric conditions (simulated altitude of 24,000 ft). Hypoxic lungs were ventilated with 5% O2-5% CO2 and control lungs with 21% O2-5% CO2. Blood gases and pH remained stable during the 1.5-h perfusion period. Exposure of normal rat lungs to 1.5 h of in vitro hypoxia (blood Po2=34 mmHg) significantly increased lactate production and mean arterial pulmonary pressure, but did not alter glucose uptake, pyruvate levels, and oxidation of either [U-14C]glucose or [1-14C]palmitate to CO2. Incorporation of labeled glucose and palmitate into lung lipids was also unaltered. In contrast to normal lungs, prior exposure to hypoxia for 24 h and subsequent perfusion under hypoxic conditions significantly stimulated glucose uptake (74% increase), markedly increased glucose incorporation into lung lipids, and increased oxidation of glucose to CO2. Lactate/pyruvate ratios also showed a significant 38% increase. Lung glycogen was unchanged following 24 h hypoxia. These data indicate that adaptive changes occur in metabolic processes within the lung during acute changes in O2 tension.     

Effect of Puromycin and Puromycin Analogues on Glycogen Synthesis in the Isolated Rat Diaphragm1

In a previous work from this laboratory it was reported that puromycin specifically depressed the insulin-induced glycogen synthesis in isolated rat diaphragm. In the present work the effect of puromycin on glycogen synthesis has been studied under modified experimental conditions. When glucose as a substrate was excluded from the incubation medium, puromycin depressed the incorporation of ¹⁴C-glucose into glycogen in absence of added insulin. To study this effect of puromycin, experiments with puromycin analogues were undertaken. At a concentration of 270 μ/ml puromycin inhibited protein synthesis by more than 0 %. Equimolar concentrations of puromycin aminonucleoside and 6-dimethylam nopurine caused only slight inhibition of protein synthesis, but depressed the incorporation of ¹⁴C-glucose into glycogen to the same degree as puromycin. The results suggest that puromycin influences the synthesis of muscle glycogen by a mechanism not related to the inhibitory efiect of puromycin on protein synthesis. The possibility that puromycin might interfere with the activity of glycogen synthetase is discussed.     

Schistosoma mansoni: effect of maintenance in vitro on the uptake and incorporation of leucine by adult worms

The rates of leucine uptake and incorporation into protein by adult male and female Schistosoma mansoni were not affected by maintenance in vitro for up to 10 days' duration, despite the decline in the protein content of male and female worms of approximately 35 and 55%, respectively, during this period. The effect of maintenance in vitro was obscured in paired female schistosomes by the apparent shielding of the female tegument within the gynaecophoral canal of the male. Incorporation rates were reduced by 50% in the presence of 2 mM cycloheximide whereas uptake rates were unaffected. Adult schistosomes are unable to maintain their in vivo protein levels purely by recourse to exogenous amino acids absorbed across the tegument in vitro, and the rates of uptake and incorporation of leucine appear to reflect the changing somatic requirements of the worms and are probably not correlated with the reproductive activity of adult worms in vitro. The possible role of alimentary rather than tegumental nutrition in egg production in vivo is discussed.     

Effect of elevated substrates on substrate oxidation in normal and diabetic aorta

The influence of elevated substrates (glucose, beta-hydroxybutyrate and palmitate) on the gated. The oxidation of 14C-glucose to 14CO2 was depressed in diabetic aorta at a glucose concentration of 5.6 mM in the incubation medium. The glucose oxidation in normal and mM. The oxidation of 14C-beta-hydroxybutyrate (0.5 and 1.5 mM) to 14CO2 was impaired in diabetic aorta, while the oxidation of 14C-palmitate (0.5 and 1.0 mM) to 14CO2 was unaltered. The oxidation of both substrates was concentration dependent. The glucose oxidation in normal rat aorta was reduced by addition of 3.0 and 6.0 mM of beta-hydroxybutyrate to the incubation medium, while 1.5 mM palmitate had no effect on the glucose oxidation. After incubation of normal rat aorta in MEM with glucose (20.0 mM) for 46 h the subsequently determined glucose oxidation was not influenced in comparison to the aorta incubated in 5.6 mM glucose. Incubation with 6.0 mM beta-hydroxybutyrate or 1.5 mM palmitate did not affect the aortic glucose oxidation. In rats which were infused for 24 h with glucose or beta-hydroxybutyrate to obtain diabetic levels of these substrates, there was no change in the aortic glucose oxidation compared to saline-infused controls. The present results suggests that the lowered glucose oxidation in diabetic vascular tissue is not caused by hyperglycemia or high concentrations of ketone bodies or free fatty acids in the diabetic state.     

Effects of glucagon and insulin on net hepatic metabolism of glucose precursors in sheep.

The net hepatic metabolism of amino glycerol, lactate, and pyruvate was determined in conscious fed sheep by multiplying the venoarterial concentration differences by the hepatic blood or plasma flow. In each experiment several sets of control blood samples were taken; glucagon or insulin then was infused intraportally for 2 h during which additional samples were taken. Four types of experiments were performed: 1) glucagon infusion (150 mug/h) into normal sheep, 2) glucagon infusion (100 mug/h) into insulin-treated alloxanized sheep, 3) insulin infusion (1.17 U/h) into normal sheep, and 4) insulin plus glucose infusion (12.3 mmol/h) into normal sheep. The second group of experiments was performed to prevent reflex hyperinsulinemia, and the fourth was performed to prevent reflex hyperglucagonemia. Glucagon directly stimulated the net hepatic uptake of alanine, glycine, glutamine, arginine, asparagine, threonine, serine, and lactate. Glucagon also stimulated lipolysis in adipose tissue. Insulin, on the other hand, appeared to have a lipogenic effect on adipose tissue and to stimulate directly the uptake of valine, isoleucine, leucine, tyrosine, lysine, and alanine only at extrahepatic sites. The study showed that, in sheep, the effects of glucagon primarily are on liver, and insulin's effects primarily are on skeletal muscle and adipose tissue where it promotes protein and lipid synthesis.     

Effects of insulin on hepatic lipid synthesis in alloxan diabetic rats.

In vitro hepatic synthesis of lipids starting from 1-(14)C-acetate was studied in rats made diabetic by subcutaneous alloxan administration (175 mg/kg b.w.). A second group of diabetic rats was treated with lente insulin. In the alloxan-treated rats, a decrese was observed in hepatic incorporation of 1-(14)C-acetate into phospholipids, triglycerides and esterified cholesterol; there was an increased incorporation into nonesterified fatty acids (NEFA) and free cholesterol. Insulin administration restored lipid synthesis values to normal. On histologic examination, an intranuclear glycogenesis was observed in the hepatocytes of the alloxan-treated rats, along with severe hepatic necrosis; the latter however, only in rats sacrified on the 3rd day. Hepatic steatosis with small, medium and large droplets was present in the insulin-treated rats; signs of cellular degeneration were less evident.