Occurrence of J blood group activities in lipid and non-lipid fractions of organs and body fluids of cattle

Total lipids and protein-containing residues obtained after lipid extraction from various organs and body fluids of J-positive cattle were tested for J activity in the bovine J blood group system. Polar lipids prepared by column chromatography of total lipids, which contain predominantly neutral lipids, were also tested. Total lipids (or polar lipids, respectively) were analysed for lipid phosphorus, lipid sugar, and hexosamine. Both lipids and non-lipid fractions of brain, myocardium, skeletal muscle, and adipose tissue show no J activity. The lipids of urinary bladder epithelium, spleen, liver, and kidney are J-positive, whereas their non-lipid fractions are J-negative. Both the lipids and the non-lipid fractions of seminal plasma, spermatozoa, and faeces are J-active. The lipids extracted from hair show no J activity, while those of cornea and eyelens are J-active. The high amount of glycolipids from seminal plasma, spermatozoa and spleen stimulates further studies of these lipids.     

Effects of a long-acting LHRH agonist preparation on plasma gonadotropin and prolactin levels in castrated male rats and on the release of prolactin from ectopic pituitaries

We have examined the effects of a single subcutaneous injection of an LHRH agonist, D-Trp-6-LHRH, in biodegradable microcapsules of poly(DL-lactide-co-glycolide) on plasma gonadotropin and prolactin (PRL) levels in castrated and in castrated-hypophysectomized-pituitary grafted (CAST-APX-GRAFT) male rats. The results were compared to the effects of daily injections of the same LHRH agonist dissolved in saline. In castrated rats, there were no significant alterations in plasma LH or PRL levels during the 10 days following the injection of LHRH agonist microcapsules, while FSH levels were generally reduced. In castrated males given daily injections of 6 micrograms of LHRH agonist in saline, plasma LH levels were significantly reduced while plasma PRL levels were not changed. In CAST-APX-GRAFT rats, both D-Trp-6-LHRH microcapsules and daily LHRH agonist injections appeared to increase plasma PRL levels. The pattern of changes in PRL release in both groups was similar, with levels on day 6 being significantly higher than those measured on days 1, 3 and 10 after onset of treatment. As expected, LH and FSH levels in these animals were extremely low. Immunoreactive D-Trp-6-LHRH was consistently detectable in the plasma of CAST-APX-GRAFT animals after microcapsule administration, whereas in animals given daily injections of this agonist in saline, its plasma concentrations were often below the detectability limit of the employed assay. These findings suggest that the LHRH agonist, D-Trp-6-LHRH, is capable of causing a short term stimulation of PRL release from ectopic pituitaries. Elevation of plasma LH levels is apparently not required for this effect.     

褪黑素抑制雌二醇诱致的垂体PRL瘤生长与血浆PRL和过氧化脂质含量的关系

雄性大鼠皮下埋置17-β雌二醇(17-β-estradiol,E2)药泵诱发垂体催乳素PRL)瘤,并每日皮下注射褪黑素(melatonin,MLT)观察MLT对E2诱发PRL瘤生长的影响.另外,采用放免法和紫外分光光度法测定大鼠血浆PRL和过氧化脂质(peroxidativelipid,PL)浓度,观察PRL瘤重量与大鼠血浆浓度间的相关关系.实验结果显示,在对照组、0.05、0.25、0.50、1.00和2.00mgMLT组,PRL瘤重量分别为115.0±71.0、85.2±41.0、58.9±24.1、72.7±23.6、79.3±56.1、74.5±46.8mg;血浆PRL浓度分别为493.46±33.3、373.78±26.5、125.13±13.3、201.79±11.2、418.88±41.3、281.94±36.4ng/ml;血浆PL水平分别为1.21±0.23、0.89±0.32、0.92±0.27、0.64±0.24、0.41±0.14、0.43±0.21△D233/ml.相关性分析表明,PRL瘤重量与血浆PRL浓度间的相关系数为0.8738(P＜0.05),与血浆PL水平间的相关系数为0.5550(P＞0.05),血浆PRL浓度与血浆PL水平间的相关系数为0.2141(P＞0.05).该结果提示,(1)0.25(P＜0.01)、0.50(P＜0.05)mgMLT能有效抑制E2诱致的PRL瘤生长和PRL分泌,所有剂量的MLT均能抑制血浆PL的形成;(2)PRL瘤重量与血浆PRL浓度间呈正相关关系,PRL瘤重量与血浆PL水平间、以及血浆PRL浓度与血浆PL水平间均无相关关系.因此,我们认为,MLT抑制E2诱致的PRL瘤生长可能与MLT抑制PRL表达性分泌有关,但与MLT抗氧化作用无关.     

Effects of Sterylglycosides from Soybean on Lipid Indices in the Plasma,Liver, and Feces of Rats

The effects of soybean oil (SOO, control), soybean lecithin (SOL), and of sterylglycocides (STG) and phospholipids (PL) fractionated from SOL on lipid indices in the plasma, liver, and feces were examined for male Wistar rats fed with diets containing these lipids for 3 weeks. The body weight gain and liver weight decreased or tended to be reduced in the animals given the diet containing a 5% STG mixture (STGM) compared with the values in the other dietary groups. The plasma lipid concentration in general declined in the rats fed with the diets supplemented with 5% SOL, STGM, or the PL mixture (PLM), and with 1% of STGM, acylated STG (ASTG), or non-acylated STG (NSTG). The triacylglycerol level was significantly depressed in the rats fed with the diets including 1 or 5% of STGM, ASTG, or NSTG when compared to the level of the SOO—fed animals. The total cholesterol and triacylglycerol contents in the liver were lower in the rats provided with the diets containing 5% of SOL, PC, or PLM than in the SOO- or STGM-diet-fed animals. The rats given the diets supplemented with 1 or 5% of STGM, ASTG, or NSTG had a decreased content of liver triacylglycerol compared with the content of the SOO—fed animals. The amounts of total lipids and total cholesterol excreted into the feces were higher in the rats fed with the diets supplemented with 5% SOL, or with 1% of STGM, ASTG, or NSTG, or especially with 5% STGM than in the SOO—fed animals. The present results suggest that STG suppressed the absorption of cholesterol and fatty acids in the intestines.     

Effects of bovine growth hormone on plasma FFA concentrations and liver, muscle and carcass lipid content in rainbow trout, Salmo gairdneri Richardson

Bovine growth hormone (GH) given daily to rainbow trout, Sulmo gairdneri for 4 or 7 days at either 10.00 or 14.00 hours, significantly increased plasma free fatty acid (FFA) levels but had not effect on plasma cholesterol levels. Liver lipid content of the GH-injected trout after seven injections was significantly lower than comparable controls in groups injected at both 10.00 and 14.00 hours. There were no apparent effects of GH on carcass or muscle lipid content although in fish injected and sampled at 14.00 hours there was a significant correlation between the number of injections and carcass lipid content.
Changes in hepatosomatic index (HSI), liver, muscle and carcass lipid content, plasma FFA and cholesterol concentrations and somatotrop activity during food-deprivation for up to 60 days are described. Despite significant decreases in liver and muscle lipid content and increases in plasma FFA levels in food-deprived fish, there was no concomitant change in apparent somatotrop activity.
The data are interpreted to indicate that although exogenous GH, in the doses used here, appears to stimulate mobilization of lipid reserves, particularly from the liver, there is no evidence that enforced changes in lipid reserves elicits a response of the endogenous somatotrop cells.     

Lipid dynamics in fish: aspects of absorption, transportation, deposition and mobilization

1. Aspects of lipid metabolism, including absorption and depositional processes, appear quite different in fish as compared to homeothermic vertebrates. 2. Dietary lipids in fish are absorbed as fatty acids and as triacylglycerols aggregated into chylomicra particles. 3. Interorgan transport of lipids, like that of mammals, consists of an exogenous (dietary) loop and an endogenous loop. 4. Fish store lipids among several depot organs, including mesenteric membranes, liver and muscle. 5. Several fast-acting and slow-acting agents modulate depot lipid mobilization. 6. Mobilized lipids may be transported in the serum as free fatty acids bound to specific carrier proteins.     

Comparative study of lipids and fatty acids in blood plasma of river lamprey Lampetra fluviatilis and brown frog Rana temporaria at the periods of elimination of exogenous feeding

Lipids of blood plasma of lampreys and frogs are composed of phospholipids, triglycerides, free fatty acids (FA), cholesterol, cholesterol esters, and waxes. The lipids content in plasma of frogs is markedly lower as compared with that of lampreys. However, the percentage of lipid components is represented by close values. Fluidity of triglycerides and phospholipids in lampreys is determined predominantly by monoenic acids and polyenoic acids of the ω-3-type, whereas that in frogs—by monoenic acids and polyenic acids of the ω-6-type. Free FA are represented mainly by saturated and monoenic acids.     

Transport, utilization and biliary secretion of lysophosphatidylcholine in the rat liver

The hepatic uptake, transport and utilization of plasma lysophosphatidylcholine (lysoPC) and its contribution to biliary lipid secretion have been investigated in bile-fistula rats. The animals were given a single intravenous dose of sn-1-[1-14C]palmitoyl-lysoPC, under constant intravenous sodium taurocholate infusion (1 mumol/min), and the fate of the label was followed in blood, bile and liver for up to 3 h. The livers were excised at given time points, extracted and/or homogenized to determine the lipid distribution and subcellular location of radioactivity. LysoPC was rapidly cleared from plasma, though a consistent fraction of the label persisted in plasma over the experimental time-period in the form of either lysoPC or PC. Recovery of radioactivity in the liver varied from 15.6% after 5 min to 19.5% after 3 h. Hepatic lysoPC underwent rapid microsomal acylation to form specific PC molecular species (mainly 16:0-20:4 and, to a lesser extent, 16:0-18:2 and 16:0-16:1). Ultrafiltration, dialysis and gel-chromatographic analyses of cytosolic fractions (post 105,000 X g supernatants) indicated that lysoPC is transported to the site of acylation mostly as a macromolecular aggregate with an approx. Mr of 14,400. Small amounts of radioactivity were secreted into bile over 3 h (20% in the form of lysoPC and the remainder as 16:0-18:2 and 16:0-20:4 PC species). Plasma lysoPC, taken up by the liver, is mostly transported by a cytosolic carrier with a molecular weight close to fatty-acid-binding proteins; it then enters a distinct acylation pathway, selective for some polyunsaturated-PC species and does not contribute significantly to biliary secretion, either directly, or through its products.     

Interaction of cells from murine organs with liposomes of various composition

The distribution of liposomes prepared from total mouse liver lipids and containing (3H)-labelled platelet activation factor in mouse organs was studied. It was shown that the majority of intraperitoneally injected liposomes prepared from total mouse liver lipids were transported to mouse liver and spleen. The interaction of liposomes with spleen cells in vitro revealed that the affinity of liposomes prepared from total spleen macrophage or total spleen lymphocyte lipids for mouse spleen cells was much higher than that of liposomes prepared from a model lipid mixture. The liposome binding to isolated spleen macrophages or lymphocytes was much higher than the liposome uptake by these cells in the total population of mouse spleen cells.     

低温暴露和恢复对棘胸蛙雌性亚成体生存力及能量物质消耗的影响

棘胸蛙(Paa spinosa)亚成体在人工驯养过程中容易出现越冬困难,非正常的冬眠可能会影响次年的繁育。以雌性棘胸蛙亚成体(1—2龄)为对象,研究该蛙在人工低温暴露(4℃保持90 d)条件下的生存力、机体能量物质消耗、肥满度、脏器系数的变化特征,以及这些参数在温度恢复至正常(由4℃缓慢升至22℃后保持7 d)后的变化情况。结果表明,该蛙在低温暴露过程中存活率逐渐降低,恢复期无死亡。肥满度(K)和体重/体长(Kwl)在低温暴露期间有逐渐升高的趋势,但两者在经历恢复期(22℃,7 d)后均恢复至初始水平(P>0.05)。胃系数和脾系数在低温暴露期呈明显的上升趋势(P<0.05),且两者在第90天均显著大于初始水平(P<0.05)。恢复期肝系数显著减小(P<0.05)。在低温暴露期各阶段肝脏和肌肉脂肪含量与初始无统计差异(P>0.05);肝脏水分在低温暴露期间呈明显下降趋势(P<0.05),而肌肉水分则与之相反;肝脏非脂肪干物质含量呈显著上升趋势(P<0.05),而肌肉非脂肪干物质则呈相反趋势。肝糖原含量随暴露时间的延长呈现显著上升趋势(P<0.05),低温暴露第60天和第90天肝糖原含量与初始相比分别增加59.4%和60.1%,而恢复期肝糖原含量则降至初始水平(P>0.05)。根据结果可以看出,在低温暴露过程中肝脏和肌肉脂肪含量变化不显著,同时肥满度、肝系数、肝脏非脂肪干物质和肝糖原含量均有不同程度的升高,而肌肉非脂肪干物质则显著减少(P<0.05),说明该蛙雌性亚成体在低温期主要消耗的能量物质不是脂肪而是肌肉非脂肪干物质,或者肌肉非脂肪干物质在组织间发生了大量转运。     

Lipid metabolism and structure-activity features of the endoplasmic reticulum membrane in regenerating rat liver]

The relationship between the neutral lipid and phospholipid metabolism and some structure-function peculiarities of regenerating rat liver endoplasmic reticulum membranes (13 hours after surgery, i.e., corresponding to the G1-period of the cell cycle) was studied. There was an increase in the degree of the endoplasmic reticulum membrane development and the nonesterified fatty acid (NFA) and triglyceride (TG) content in regenerating rat liver microsomes. The relative specific radioactivity of neutral lipid and phospholipid fractions in regenerating rat liver microsomes was lower than in control animals, presumably due to the high rate of the microsomal lipid exchange in the regenerating liver with other cell organelles. The changes in the lipid content and rate of their metabolism in the regenerating rat liver were associated with the increase in the membrane microviscosity and the decrease in the activity of the membrane-bound enzyme (glucose-6-phosphatase). The differences in the time-dependent changes in the synthesis and metabolism of lipids in the NFA and TG fractions may be regarded as an endogenous factor determining the structure-function peculiarities of endoplasmic reticulum membranes.     

Osmotic and metabolic responses to dehydration and urea-loading in a dormant,terrestrially hibernating frog

Physiological responses to dehydration in amphibians are reasonably well documented, although little work has addressed this problem in hibernating animals. We investigated osmotic and metabolic responses to experimental manipulation of hydration state in the wood frog (Rana sylvatica), a terrestrial hibernator that encounters low environmental water potential during autumn and winter. In winter-conditioned frogs, plasma osmolality varied inversely with body water content (range 69–79%, fresh mass) primarily due to increases in sodium and chloride concentrations, as well as accumulation of glucose and urea. Decreased hydration was accompanied by a marked reduction in the resting rate of oxygen consumption, which was inversely correlated with plasma osmolality and urea concentration. In a separate experiment, resting rates of oxygen consumption in fully hydrated frogs receiving injections of saline or saline containing urea did not differ initially; however, upon dehydration, metabolic rates decreased sooner in the urea-loaded frogs than in control frogs. Our findings suggest an important role for urea, acting in concert with dehydration, in the metabolic regulation and energy conservation of hibernating R. sylvatica.     

The effect of dehydration on the functional activity of the interrenal gland in adenohypophysectomized Rana catesbeiana frogs. A preliminary report

A significant increase of the content of corticosterone in the blood collected from intravenous cannula or by intracardiac punction has been detected using radioimmunoassay in non-operated and adenohypophysectomized frogs Rana catesbeiana subjected to dehydration in 6.2% mannitol solution during 24 hours. The osmolality of the blood plasma of these animals also increases although less significantly than the growth of plasma corticosterone content. There is a tendency to substantial increase of plasma arginine-vasotocin level prior to the growth of corticosterone level, already after 6 hours of dehydration. Based on the present results and literature data, it is suggested that in adenohypophysectomized frogs lacking endogenous ACTH just the increase of blood arginine-vasotocin level results in a substantial activation of corticosteroid-producing cells of the interrenal gland and in the growth of plasma content of corticosterone.     

Some effects of morphine on lipid metabolism in normal,tolerant and abstinent rats

The effects of morphine on lipid levels of plasma and liver were studied in rats. The first injection of morphine induced a decrease in free fatty acids (FFA) and an increase in the plasma triglyceride level. No changes in phospholipid, cholesterol or cholesterol ester concentrations were observed. In chronic morphinized rats the plasma FFA level was unchanged one hour following the injection of morphine and tolerance developed to the depressive effect of the drug. In contrast, the rise in plasma triglycerides persisted, but to a lesser extent. In these animals, the plasma levels of FFA and of triglycerides were lower than in normal rats, when blood was sampled 24 hours after the last injection of morphine. In abstinent rats, a reversal of action of morphine was noticed. Nalorphine induced an increase in plasma FFA levels in normal and abstinent rats but not in chronically morphine-treated animals. In the liver no significant changes occured in lipids in either acute or chronically morphinized rats. The effects of morphine on plasma lipid levels might be linked to the action of the drug on the secretory activity of the adrenals and also to the depressive effect of the drug on the lipolytic activity of adipose tissue which was demonstrated in vitro.     

Influence of the antioxidant status on the characteristics of lipids in tissues of animals after acute irradiation with sublethal doses

The effect of the acute exposure to sublethal doses of X-rays on the interrelation between parameters of the lipid peroxidation regulatory system (lipid antioxidative activity, AOA; peroxide amount, lipid composition) was studied in liver, spleen and blood erythrocytes of CBA and SHK mice and rats within 1 month after irradiation. The reverse correlation between the lipid AOA values and the initial peroxide amount in lipids of the CBA mice spleen was found. The coefficient of the linear regression of this correlation for the exposed mice was 1.8-fold higher as compared with control. The correlative dependence between the ratio of the sums of the more readily to more poorly oxidizable phospholipid and the ratio of phosphatidyl choline to phosphatidyl ethanolamine content in phospholipids of liver and blood erythrocytes was revealed. The direction (the phospholipids of the rat liver) or the value of the linear regression coefficient of that correlation were different for groups of the exposed and control animals, especially in the blood erythrocytes. Thus, the different sensitivity of examined characteristics of lipids and the possibility of their normalization in the dependence on the lipid AOA value cause the conversion of the lipid peroxidation regulatory system in organs and blood erythrocytes of the exposed animals to the other scale of the functioning.     

Diurnal variations of plasma lipoproteins and liver lipids in rats fed starch sucrose or fat

The incidence of the dietary source of energy on lipid transport and accumulation was investigated over a full nycthemeral cycle in adapted rats fed ad libitum. Starch, sucrose and lard were compared. Lipoprotein composition of the plasma, liver and plasma lipids and insulinemia were analyzed every 3 hours over 24 hours. The pattern of VLDL concentration was dependent on the nature of the energetic substrate. Feeding starch resulted in a remarkable stability of lipoproteins, liver and plasma lipids, despite clearcut diurnal variations in plasma non esterified fatty acids, insulinemia and liver glycogen. In sucrose-fed rats VLDL rose to a sharp maximum in the post prandial period (9-12:00) and were totally cleared by 18:00. In fat-fed rats, HDL were elevated during the night, suggesting a possible stimulation of their synthesis by dietary fat in the intestine. LDL were constantly elevated with peak values at 21:00 while VLDL were very low, even at night, despite elevated levels of non-esterified fatty acids. It is concluded that, in animals adapted to a high fat-diet, a high level of circulating non esterified fatty acids is not sufficient to promote the synthesis of VLDL. The main regulating factor appears to be the intensity of hepatic lipogenesis which is stimulated by sucrose and inhibited by lard. No correlation was found between variations in plasma VLDL and insulinemia.     

The importance of glucose for the freezing tolerance/intolerance of the anuran amphibians Rana catesbeiana and Bufo paracnemis

Several species of terrestrially hibernating frogs, turtles and insects have developed mechanisms, such as increased plasma glucose, anti-freeze proteins and antioxidant enzymes that resist to freezing, for survival at subzero temperatures. In the present study, we assessed the importance of glucose to cryoresistance of two anuran amphibians: the frog Rana catesbeiana and the toad Bufo paracnemis. Both animals were exposed to -2 degrees C for measurements of plasma glucose levels, liver and muscle glycogen content, haematocrit and red blood cell volume. Frogs survived cold exposure but toads did not. Blood glucose concentration increased from 40.35 +/- 7.25 to 131.87 +/- 20.72 mg/dl (P < 0.01) when the frogs were transferred from 20 to -2 degrees C. Glucose accumulation in response to cold exposition in the frogs was accompanied by a decrease (P < 0.05) in liver glycogen content from 3.94 +/- 0.42 to 1.33 +/- 0.36 mg/100 mg tissue, indicating that liver carbohydrate reserves were probably the primary carbon source of glucose synthesis whereas muscle carbohydrate seems unimportant. In the toads, the cold-induced hyperglycaemia was less (P < 0.05) pronounced (from 27.25 +/- 1.14 to 73.72 +/- 13.50 mg/dl) and no significant change could be measured in liver or muscle glycogen. Cold exposition had no effect on the haematocrit of the frogs but significantly reduced (P < 0.01) the haematocrit of toads from 20.0 +/- 2.1% to 5.8 +/- 1.7% due to a decreased red blood cell volume (from 1532 +/- 63 to 728 +/- 87 mm3). When toads were injected with glucose, blood glucose increased to levels similar to those of frogs and haematocrit did not change, but this failed to make them cryoresistent. In conclusion, the lack of cold-induced glucose catabolism may not be the only mechanism responsible for the freeze intolerance of Bufo paracnemis, a freeze-intolerant species.     

Incorporation of dietary cis and trans isomers of octadecenoate in lipid classes of liver and hepatoma.

Groups of rats bearing Morris minimal deviation hepatoma 7288CTC were fed a fat-free diet supplemented with either 0.5% safflower oil (diet A), 15% safflower oil or free acids (diets Band C), or 15% safflower oil or free safflower fatty acids (diet D) for 4 weeks. A group of normal rats was also fed diet D. Triglycerides, cholesteryl esters, phosphatidylcholines, and phosphatidylethanolamines isolated from livers and hepatomas of animals on each diet were analyzed quantitatively for positional isomers in the cis- and trans-octadecenoate fractions. When sufficient samples could be obtained, the cis- and trans-hexadecenoate fractions were also analyzed. Plasma from normal rats on diet D was analyzed in the same manner. The octadecenoate fractions of all hepatoma and liver lipid classes from animals fed diets A, B, and C were greater than 95% the cis isomers. Trans isomers accounted for approximately 15, 30, 50, and 70% of the octadecenoate fractions isolated from liver triglycerides, cholesteryl esters, phosphatidylcholines, and phosphatidylethanolamines, respectively, of animals fed diet D. In contrast, all hepatoma lipid classes from animals on diet D contained the same approximate percentage of trans isomers (15 to 20%). Oleic and vaccenic acids were the major positional cis-octadecenoate isomers of all liver and hepatoma lipid classes from animals fed diets A, B, and C. The ratios of oleic to vaccenic, unaffected by diets A, B, and C, differed for each lipid class in liver, but the ratios were similar for the two hepatoma neutral lipid classes and for the two phospholipid classes. The cis-octadecenoate fractions from all liver and hepatoma lipid classes of animals fed diet D consisted predominantly of the delta9, delta11, and delta12 isomers. The cis delta10 isomer, which was a major isomer of the diet, was almost excluded from liver, hepatoma, and plasma lipids. The positional isomers of the trans-octadecenoate fractions from liver and hepatoma triglycerides and cholesteryl esters exhibited the same approximate distribution as the trans fatty acids of diet D. In contrast, the 10-trans-octadecenoate, like 10-cis-octadecenoate, was almost excluded from the phospholipids of liver and plasma. Unlike liver, the hepatoma phospholipids contained 10-trans-octadecenoate at approximately half the percentage of neutral lipids. Because diet D contained no hexadecenoic fatty acids, the occurrence of trans-hexadecenoate isomers in liver and plasma lipids indicated a chain shortening process. Predominance of the 8-trans-hexadecenoate isomer indicated a preference of the 10-trans-octadecenoate isomer for chain shortening.     

Effect of experimentally induced hyperprolactinemia on growth hormone secretion

In order to study the existence of possible interrelation-ships between prolactin (PRL) and growth hormone (GH) secretions, adult male rats bearing an anterior pituitary graft under the kidney capsule since day 90 of life and their sham-operated controls were submitted to a single i.p. administration of L-dopa (50 mg/kg weight) or saline 30 days after the operation. Plasma PRL and GH levels were measured by using specific RIA methods. Dopamine (DA) and norepinephrine (NE) contents in the hypothalamus and in the in situ anterior pituitary gland were measured by using a specific radioenzymatic assay. An increase in plasma PRL levels and a decrease in plasma GH levels were shown in grafted rats. Hypothalamic contents of DA and NE were increased in these animals, while the anterior pituitary content of DA was not modified as compared to controls. The administration of a single injection of L-dopa led to decreases of plasma PRL and GH levels in both grafted and control rats, but while marked increases in hypothalamic and anterior pituitary contents of DA were shown in both groups, the hypothalamic content of NE was only increased in control animals. These data suggest that PRL and GH secretions were closely related. Dopamine could be mediating the action of PRL on GH, while NE would be less involved.     

The effect of high-fat diet and inhibition of ceramide production on insulin action in liver

Liver, as one of the most important organs involved in lipids and glucose metabolism, is perceived as a key tissue for pharmacotherapy of insulin resistance (IRes) and type 2 diabetes. Ceramides (Cer) are biologically active lipids, which accumulation is associated with the induction of muscle IRes. We sought to determine the role of intrahepatic bioactive lipids production on insulin action in liver of insulin-resistant rats and after myriocin administration. The experiments were conducted on male Wistar rats divided into three groups: Control, fed high-fat diet (HFD), and fed HFD and treated with myriocin (HFD/Myr). Before sacrifice, the animals were infused with a [U-¹³C]palmitate to calculate lipid synthesis rate by means of tracer incorporation technique in particular lipid groups. Liver Cer, diacylglycerols (DAG), acyl-carnitine concentration, and isotopic enrichment were analyzed by LC/MS/MS. Proteins involved in lipid metabolism and insulin pathway were analyzed by western blot analysis. An OGTT and ITT was also performed. HFD-induced IRes and increased both the synthesis rate and the content of DAG and Cer, which was accompanied by inhibition of an insulin pathway. Interestingly, myriocin treatment reduced synthesis rate not only of Cer but also DAG and improved insulin sensitivity. We conclude that the insulin-sensitizing action of myriocin in the liver is a result of the lack of inhibitory effect of lipids on the insulin pathway, due to the reduction of their synthesis rate. This is the first study showing how the synthesis rate of individual lipid groups in liver changes after myriocin administration.