Effects of surgical stress on the response of hepatic carnitine metabolism to 48 h starvation in the rat.

Rats subjected to laparotomy and handling of the liver were starved for 48 h, starting either immediately after surgery or 48 h later. Surgery enhanced the rise in plasma non-esterified fatty acid concentrations after starvation without affecting the responses of blood or liver ketone bodies. Thus in surgically stressed rats, blood and liver ketone body concentrations were inappropriately low for the blood fatty acid concentrations. In the control rats, starvation increased hepatic carnitine concentrations, mainly through increases in short-chain acylcarnitine. Surgical stress decreased or abolished these increases. This may possibly contribute to the blunted ketonaemic response observed after surgery.

Liver carnitine metabolism after partial hepatectomy in the rat. Effects of nutritional status and inhibition of carnitine palmitoyltransferase.

This study examined the effects of partial hepatectomy on hepatic carnitine and acylcarnitine concentrations in fed or 24 h-starved partially hepatectomized (PH) or sham-operated (SO) rats at 1 or 4 days after surgery. The ratio of free to esterified carnitine was low in fed PH rats at day 1: the low ratio was increased to the SO value when mitochondrial fat oxidation was inhibited by 2-tetradecylglycidate. Starvation (24 h) increased plasma [non-esterified fatty acid] in PH or SO rats, the increases being greater at day 1 than at day 4. Hepatic [long-chain acylcarnitine] were also increased. These latter increases were a consequence of increased mitochondrial fat oxidation since they were not observed in PH or SO rats treated with 2-tetradecylglycidate. Whereas the starvation-induced increase in long-chain acylcarnitine was associated with increased [ketone body] in livers of SO rats at both day 1 and day 4 after surgery, [ketone body] was inappropriately low for the steady-state long-chain [acylcarnitine] in livers of PH rats at the first post-operative day. This was not a consequence of a decrease in [total carnitine] in the liver. The results are discussed with reference to the role of the liver in determining the relative proportions of the fat fuels available for extrahepatic tissues and the effects of liver cell proliferation on hepatic triacylglycerol metabolism.

Mechanism of the inhibitory effect of trifluoperazine on isoprenaline-evoked amylase secretion from isolated rat parotid glands.

We have investigated the effects of the calmodulin antagonist trifluoperazine (TFP) on amylase secretion and adenosine 3':5'-monophosphate (cyclic AMP) metabolism using incubated parotid glands of young rats. Exposing unstimulated glands to 100 microM TFP doubled the basal rate of amylase and lactate dehydrogenase (LDH) release, but had no effect on either the parotid cyclic AMP or ATP contents. Isoprenaline (1 microM) stimulated amylase secretion and increased the tissue cyclic AMP content. 100 microM TFP inhibited these responses by 46% and 33%, respectively. N6,O2-dibutyryl adenosine 3',5'-monophosphate (dibutyryl cyclic AMP) mimicked the effect of isoprenaline on amylase release but 100 microM TFP had no effect on this response. 10 microM TFP inhibited F- -stimulated adenylate cyclase activity in a subcellular fraction isolated from the parotid by 32%. We conclude that TFP may inhibit isoprenaline-evoked amylase secretion from the rat parotid by an effect on either the catalytic or regulatory subunits of adenylate cyclase.

Crohn's disease of the gall bladder.

A 64 year old man with known enteric Crohn's disease developed a granulomatous cholecystitis in which the histological features were identical to those seen in sites conventionally affected by this disease. Extraintestinal granulomatous lesions are rare in Crohn's disease and the present case is reported because of its apparent uniqueness.

Control of tissue carnitine contents: effects of partial hepatectomy and liver regeneration on carnitine concentrations in liver and extrahepatic tissues of the rat.

The liver is the sole site of carnitine biosynthesis in the rat. However, the first 24 h after the surgical removal of two-thirds of the liver mass are not associated with depletion of carnitine either in the liver remnant or in a number of extrahepatic tissues with relatively short turnover times of carnitine (less than 24 h; heart, spleen, kidney). Dietary carnitine was not supplied. The results suggest that the capacity of the remnant liver for carnitine biosynthesis is sufficient to maintain tissue carnitine contents. Liver regeneration influenced the relative proportions of hepatic free and acylated carnitines in a manner compatible with changes in fat disposition in the proliferating tissue.

Altered interactions between glycogenesis and lipid synthesis after liver resection: specific effects of liver regeneration, coupled with non-specific effects of surgery.

1. This work investigated the relationship between glycogenesis and lipid synthesis during liver regeneration after partial hepatectomy in the rat. 2. Rates of lipid synthesis were increased during the first 2 post-operative days; these elevated rates were unaffected by starvation. By contrast, glycogen concentration were decreased even after 8 post-operative days, by which time liver mass had been restored and concentrations were sensitive to nutritional status. 3. The results of experiments involving the intragastric or intraperitoneal administration of glucose indicated that increased lipid synthesis was unlikely to be a consequence of decreased glycogenesis, but that depletion of liver glycogen might be linked both to liver cell division and, in the longer term, surgical stress.

Hormonal regulation of fat esterification & oxidation in hepatocytes from fed rats: modulation by 3-mercaptopicolinate.

3-Mercaptopicolinate, an inhibitor of phosphoenolpyruvate carboxykinase (PEPCK), decreased esterification of [1-14C] oleate and [1-14C] myristate in hepatocytes from fed rats. In the absence of 3-mercaptopicolinate, adrenaline, noradrenaline, vasopressin or angiotensin II increased esterification to triacylglycerol of [1-14C] oleate but not [1-14C] myristate. Cyclic AMP decreased esterification of both oleate and myristate. In the presence of 3-mercaptopicolinate, stimulation of oleate esterification by the catecholamines, vasopressin or angiotensin II was increased, and stimulatory effects of these hormones on myristate esterification were observed. Adrenaline, noradrenaline, vasopressin or angiotensin II increased 14CO2 production from both [1-14C] oleate and [1-14C] myristate but the degree of stimulation was similar in the absence or presence of 3-mercaptopicolinate. The results indicate a role for the catecholamines and angiotensin II in the regulation of liver fat metabolism and emphasize the potential importance of changes in activity of PEPCK as determinants of hepatic carbon flux.

Ketone-body metabolism after surgical stress or partial hepatectomy. Evidence for decreased ketogenesis and a site of control distal to carnitine palmitoyltransferase I.

Rats were subjected to laparotomy, or laparotomy and partial hepatectomy, at 0-48 h before administration of water or medium-chain-length triacylglycerol, having been starved post-operatively. Functional hepatectomies were performed at intervals after the intragastric load. Blood ketone-body concentrations after medium-chain triacylglycerol administration and/or functional hepatectomy of these rats were compared with values obtained in starved control rats. Decreased ketonaemia in response to medium-chain triacylglycerol was observed for up to 48 h after partial hepatectomy and at 1 and 2 h after laparotomy, but not at 24 or 48 h after laparotomy. Rates of ketone-body clearance after functional hepatectomy were unaffected by prior laparotomy or partial hepatectomy. Ketonaemia after medium-chain-triacylglycerol administration was only partially blocked by inhibition of CPT I (carnitine palmitoyltransferase I). The results demonstrate sustained effects of partial hepatectomy and short-term effects of surgical stress to decrease ketonaemia via inhibition of ketogenesis at site(s) distal to CPT I.

Hormonal regulation of ketogenesis in hepatocytes from fed rats before and after glycogen depletion.

Vasopressin, angiotensin II and the catecholamines decreased ketogenesis from oleate but increased ketogenesis from butyrate in hepatocytes from fed rats. The hormones increase CO2 production from both oleate and butyrate. It is suggested that whereas the mitochondrial uptake of butyrate is linked to its rate of oxidation, that of oleate is independent of its intramitochondrial metabolism, and consequently the oxidation of oleate to CO2 occurs at the expense of ketogenesis. Effects of the hormones on ketogenesis from oleate or butyrate were not observed after pre-treatment of the hepatocytes with dibutyryl cyclic AMP for 1 hour. The insensitivity of ketogenesis to the hormones after this treatment (which mimics the effects of acute carbohydrate deprivation in vivo) questions the physiological significance of hormonal regulation of ketogenesis other than at the onset of starvation.

Hepatic pyruvate metabolism during liver regeneration after partial hepatectomy in the rat.

Hepatic pyruvate kinase (PK) and pyruvate dehydrogenase (PDHa) specific activities were decreased after partial hepatectomy or sham operation. The decreases were more marked and sustained after partial hepatectomy. These activity changes ensure that hepatic carbon flux after partial hepatectomy is predominantly in the direction of gluconeogenesis. The decrease in PK specific activity observed after partial hepatectomy was associated with a decreased PK activation ratio (activity measured at 0.15 mM PEP: activity measured at 5.0 mM PEP), and hepatic concentrations of PEP were increased. The low hepatic PDHa activity observed at the first day after partial hepatectomy occurred concomitantly with an increased fatty acid concentration. PDHa activity increased after inhibition of lipolysis. The results indicate that carbohydrate utilization is unimportant for hepatic energy supply during liver regeneration. There was no evidence that the control of PK or PDH in the regenerative liver after partial hepatectomy differed from that observed in the liver of the unoperated rat.

The effects of surgical stress and short-term fasting on protein synthesis in vivo in diverse tissues of the mature rat.

1. We measured fractional rates of protein synthesis, capacities for protein synthesis (i.e. RNA/protein ratio) and efficiencies of protein synthesis (i.e. protein-synthesis rate relative to RNA content) in fasted (24 or 48 h) or fasted/surgically stressed female adult rats. 2. Of the 15 tissues studied, fasting caused decreases in protein content in the liver, gastrointestinal tract, heart, spleen and tibia. There was no detectable decrease in the protein content of the skeletal muscles studied. 3. Fractional rates of synthesis were not uniformly decreased by fasting. Rates in striated muscles, uterus, liver, spleen and tibia were consistently decreased, but decreases in other tissues (lung, gastrointestinal tract, kidney or brain) were inconsistent or not detectable, suggesting that, in many tissues in the mature rat, protein synthesis was not especially sensitive to fasting. 4. In fasting, the decreases in fractional synthesis rate resulted from changes in efficiency (liver and tibia) or from changes in efficiency and capacity (heart, diaphragm, plantaris and gastrocnemius). In the soleus, the main change was a decrease in capacity. 5. Surgical stress increased fractional rates of protein synthesis in diaphragm (where there were increases in both efficiency and capacity) by about 50%, in liver by about 20%, in spleen by about 40%, and possibly also in the heart. In liver and spleen, capacities were increased. In other tissues (including the skeletal muscles), the fractional rates of protein synthesis were unaffected by surgical stress.

Altered interactions between lipogenesis and fatty acid oxidation in regenerating rat liver.

The concentrations of malonyl-CoA, citrate, ketone bodies and long-chain acylcarnitine were measured in freeze-clamped liver samples from fed or starved normal, partially hepatectomized or sham-operated rats. These parameters were used in conjunction with measurements of the concentration of plasma non-esterified fatty acids and the rates of hepatic lipogenesis to obtain correlations between rates of fatty acid delivery to the liver, lipogenesis and fatty acid oxidation to ketone bodies and CO2. These correlations indicated that the development of fatty liver after partial hepatectomy is due to an increased partitioning of long-chain acyl-CoA towards acylglycerol synthesis and away from acylcarnitine formation. However, this did not appear to be due to an altered relationship between hepatic malonyl-CoA concentration and acylcarnitine formation. For any concentration of long-chain acylcarnitine, the concentrations of both hepatic and blood ketone bodies were significantly lower in partially hepatectomized rats than in normal or sham-operated animals. This indicated that a lower proportion of the product of beta-oxidation was used for ketone-body formation and more for citrate synthesis in the regenerating liver, especially during the first 24 h after resection. This inference was supported by the changes in hepatic citrate concentrations observed. The high rates of lipogenesis that occurred in the liver remnant were accompanied by an altered relationship between lipogenic rate and hepatic malonyl-CoA concentration, such that much lower concentrations of malonyl-CoA were associated with any given rate of lipogenesis. These adaptations are discussed in relation to the requirements by the remnant for high rates of energy formation through the tricarboxylic acid cycle during the first 24 h after resection, and the possibility that cycling between fatty acid oxidation and synthesis may occur to a greater degree in regenerating liver.

Ketone-body metabolism after partial hepatectomy in the rat.

Fed or 24 h-starved rats were subjected to two-thirds partial hepatectomy or sham-operation and subsequently starved for 4, 14 or 24 h. Despite high plasma fatty acid concentrations, the partially hepatectomized rats failed to respond to post-operative starvation with increased blood and liver ketone-body concentrations or to maintain the high ketone-body concentrations associated with pre-operative starvation. Hypoglycaemia and hyperlactaemia were observed within 30 min of functional hepatectomy, but not partial hepatectomy, of 24 h-starved rats, and, even after a further 24 h starvation of partially hepatectomized rats, blood glucose concentrations were only slightly decreased. The results are discussed with reference to fat oxidation and gluconeogenesis in the liver remaining after partial hepatectomy.

Protein synthesis in liver and extra-hepatic tissues after partial hepatectomy.

Effects of partial hepatectomy on protein synthesis were defined in liver and extra-hepatic tissues of the mature rat. Studies were performed at 24 h and 48 h after surgery in the absence of the dietary input. Protein accretion in the regenerating liver preceded mitosis, but was accompanied by increases in RNA content and fractional rates of protein synthesis (ks). A positive relationship existed between protein-synthetic capacity and ks over the period of study. Increases in ks also bore a positive relationship with increases in translational efficiency. Extra-hepatic tissues showing decreased rates of protein synthesis after liver resection included kidney, striated muscles and brain. Effects were observed mainly at 24 h after surgery and resulted from decreased translational efficiency. Partial hepatectomy increased ks in diaphragm and tibia at both 24 h and 48 h after surgery. In diaphragm, there was net protein accretion, and, as in liver, increases in ks were due to increases in both protein-synthetic capacity and efficiency.

The relationship between fat synthesis and oxidation in the liver after re-feeding and its regulation by thyroid hormone.

The administration of glucose to 48 h-starved euthyroid or hyperthyroid rats led to decreased blood concentrations of fatty acids and ketone bodies in both groups, but fatty acid concentrations were higher and ketone-body concentrations lower in the latter group. Decreased ketonaemia was not due to increased ketone-body clearance. Flux through carnitine palmitoyltransferase 1 was increased, consistent with the effects of hyperthyroidism on enzyme activity demonstrated in vitro. Correlations between the concentrations of ketone bodies and long-chain acylcarnitine measured in freeze-clamped liver samples indicated that a lower proportion of the product of beta-oxidation was used for ketone-body synthesis. Citrate concentrations were unaffected by hyperthyroidism, but lipogenesis was increased. The results are discussed in relation to the factors controlling hepatic carbon flux and energy requirements after re-feeding.

Activities of cardiac and hepatic pyruvate dehydrogenase complex are decreased after surgical stress.

The work investigated the effects of surgical stress on the activities of cardiac and hepatic pyruvate dehydrogenase complex (active form, PDHa) in fed rats. PDHa activities in heart and liver were decreased within 4h of surgery with maximum inhibition at 24h after surgery. PDHa activities remained low until the fourth (liver) and eighth (heart) post-operative days. The decreased activities found at 4h and 24h after surgery were associated with increased plasma fatty acid concentrations, and inhibition of lipolysis resulted in reactivation of the enzyme complex. The results are discussed with reference to the control of pyruvate dehydrogenase activities by the oxidation of fat fuels and multisite phosphorylation in stress states, and its possible importance in glucose conservation after surgery and trauma.