Low Protein-fed Rats Research Articles

Dugotrajna primena hlorokina i etanola izaziva ozbiljna morfološka oštećenja bubrega kod pacova na niskoproteinskom režimu ishrane

The aim of the study was to investigate the microscopic renal changes resulting from the concurrent administration of chloroquine and ethanol, with inadequate dietary protein using rats. Sixty-four rats were randomly distributed into eight groups of eight rats each: control groups on normal protein (NPC) or low protein diet (LPC); chloroquine treatment groups on normal protein (NPQ) or low protein diet (LPQ); ethanol treatment groups on normal protein (NPE) or low protein diet (LPE); concurrent chloroquine and ethanol treatment groups on normal protein (NPQE) or low protein diet (LPQE). Chloroquine in 0.9% normal saline was administered weekly to NPQ, LPQ, NPQE, and LPQE. While NPE, LPE, NPQE and LPQE received 6% ethanol in drinking water ad libitum, NPC and LPC received 0.9% normal saline and plain drinking water. After treatment, routine haematoxylin and eosin stain, Masson's trichrome stain for collagen, kidney volume estimation, glomeruli count, immunofluorescence for aquaporin 2 and urine volume estimation were conducted. The results showed a decreased kidney volume in all the experimental groups compared to the control. There was increased collagen fiber deposition and distortion of renal histology in the experimental groups compared to control. Concurrent administration of chloroquine and alcohol causes distortion of kidney histology and derangements of renal function in the low protein-fed rats and can cause kidney failure.

Apigenin alleviated acetaminophen-induced hepatotoxicity in low protein-fed rats: Targeting oxidative stress, STAT3, and apoptosis signals.

Apigenin (API) is a natural flavonoid abundant in fruits and vegetables. The present study was undertaken to evaluate the effect of protein malnutrition (PMN) on acetaminophen (APAP)-induced hepatotoxicity, together with the protective effects of API, in male Wistar albino rats. In total, 64 male rats were divided into eight groups. Silymarin (SIL) (100 mg/kg, PO) as a reference standard and API (50 mg/kg, PO) were given to normal and APAP-induced hepatic injury in low protein-fed rats. The present results revealed that PMN significantly potentiated APAP-induced hepatotoxicity. Interestingly, the administration of SIL and API alleviated the induced damage, as revealed by reduced serum alanine aminotransferase and aspartate aminotransferase activities along with a significant improvement of the histopathological damage. API suppressed inflammatory response by reducing the interleukin-1β level and signal transducer and activator of transcription 3 expressions along with attenuating oxidative stress as shown by a significant reduction in liver contents of malondialdehyde and nitrite/nitrate as well as restoration of hepatic content of reduced glutathione and superoxide dismutase activity. API also counteracted apoptosis through downregulation of caspase-3 expression level. In conclusion, PMN greatly potentiated the hepatotoxic effects of APAP, and API produced a multimechanistic hepatoprotective activity that can be attributed to its antioxidant, anti-inflammatory, and antiapoptotic effects.

H+-ATPase Activity in Collecting Duct Segments in Protein-Deprived Rats – Role of Angiotensin II on Its Regulation

Background: Enhanced expression of the genes that encode for components of the renin-angiotensin system (RAS) has been exhibited in low-protein-fed (LP) rats. We examined distal proton secretion in LP rats through the activity of H⁺-ATPase on microdissected CCD, OMCD and IMCD segments. The effect of angiotensin II AT₁ receptor inhibition and protein recovery (24% protein) on H⁺-ATPase activity was studied. Methods: Bafilomycin-sensitive H⁺-ATPase activity on CCD, OMCD and IMCD segments of LP (protein 8%) and control rats CP (protein 24%) was evaluated. We examined the levels of mRNA expression of RAS components: angiotensin-converting enzyme (ACE), angiotensinogen and angiotensin II AT₁ expression; AT₁receptor binding and distribution were determined by quantitative autoradiography. Results: Increased ACE and AT₁ mRNA expression was found in cortex and medulla of LP compared to NP rats. AT₁ receptor binding density was significantly reduced in renal cortex and inner stripe of the outer medulla of LP compared to NP rats. Minimal radioligand binding was shown in inner medulla of LP. Whole kidney expression of angiotensinogen was unaltered in LP. H⁺-ATPase activity significantly decreased in IMCDs and OMCDs of LP. The inhibitory effect of LP was abolished when OMCD segments were incubated for 60 min in the presence of losartan 10^–6 to 10^–8M. There was no effect of losartan concentrations from 10^–6 to 10^–8 M on IMCDs. Similar results were observed on H⁺-ATPase activity in OMCD and IMCD segments after readministration of 24% protein in the diet. Conclusion: Both the recovery of H⁺-ATPase activity in OMCD segments induced by losartan and the increased expression of AT₁receptor suggest angiotensin II modulation of proton ATPase activity on this duct segments in LP rats. Intense compromise of proton secretion through the continued H⁺-ATPase inhibition in IMCDs from LP was shown.

Hepatic branched-chain alpha-keto acid dehydrogenase complex in female rats: activation by exercise and starvation.

The effects of acute exercise and starvation on hepatic branched-chain alpha-keto acid dehydrogenase (BCKDH) complex activity were examined in female rats fed high (30%)- or low (8%)-protein diets. The total activity of the complex was significantly higher in the high protein-fed rats than in the low protein-fed rats but was not affected by acute exercise and starvation in either diet group. The proportion of the active form of BCKDH complex was less than 10% in both diet groups. Acute exercise and starvation markedly increased the active form of the complex in both diet groups. The activity of BCKDH kinase, which is responsible for inactivation of the BCKDH complex by phosphorylation, tended to be decreased by acute exercise and starvation in both diet groups. These results suggest that the activity of the BCKDH kinase is an important factor determining the proportion of the active form of BCKDH complex in exercise and starvation, and that the female rat is a useful model for studying the regulation of hepatic BCKDH complex activity.

Role of glucocorticoids in programming of maternal diet-induced hypertension in the rat

A rat model of hypertension induced by in utero exposure to maternal low protein diets has previously been described. Low protein exposed rat pups are of lower weight at birth and have large associated placentas. Such animals are proposed, therefore, to mirror individuals in the human population perceived to be at greater risk of cardiovascular disease in adulthood. Recent work has suggested that maternal glucocorticoids may programme this increased risk of later disease. The role of glucocorticoids in programming the hypertensive state was assessed by administration of the 11β-hydroxylase inhibitor, metyrapone, to pregnant rats consuming 18 (control) or 9% (low protein) casein diets. At day 14 of pregnancy, fetuses and placentas of low protein-fed rats were significantly larger than those of controls. Metyrapone significantly inhibited corticosterone synthesis in both dietary groups, and attenuated the more rapid growth of fetus and placenta in the low protein fed group. Systolic blood pressures of rats exposed to the low protein diet in utero were significantly higher (29 mmHg) than those exposed to the control diet. Metyrapone abolished the hypertensive state of low protein exposed rats, but in the control group significantly elevated blood pressure by 15 mm Hg. Maternal and fetal glucocorticoid interactions in utero clearly have an important role in determining future regulation of blood pressure. Maternal-diet induced hypertension in the rat would appear to be a glucocorticoid-dependent phenomenon.

Membrane and cytosolic protein phosphorylation patterns in the early stages of DEN-induced hepatocarcinogenesis in rats fed a high or low protein diet.

The membrane and cytosolic protein phosphorylation patterns in the early stages of diethylnitrosamine-induced rat liver carcinogenesis, promoted by 2-acetylaminofluorene in the diet plus partial hepatectomy (DEN-AAF-PH), were analyzed by two-dimensional gel electrophoresis in animals fed a low protein (5% casein) diet, or the original high protein (24% casein) diet, in order to modulate the development of GST-P-positive preneoplastic lesions. Compared with untreated controls, membrane and cytosolic protein phosphorylation patterns changed only slightly in low protein-fed rats 7 days post-hepatectomy, with no appearance of enzyme-altered hyperplastic foci in the liver sections. By contrast, high protein-fed animals demonstrated GST-P-positive preneoplastic lesions 7 days post-hepatectomy and several acidic and more basic high M(r) phosphorylated membrane (between 97 and 116 kDa) as well as cytosolic (between 97 and 200 kDa) proteins could be detected. In the presence of enzyme-altered hepatocytes in the liver sections, low protein-fed rats demonstrated at 60 days post-hepatectomy cytosolic protein phosphorylation patterns remarkably similar to those shown by 24% casein-fed animals at 7 days post-hepatectomy, suggesting close correlation between protein phosphorylation patterns and development of preneoplastic lesions during the early stages of DEN-AAF-PH liver carcinogenesis. This may arise by a constitutive activation of one or more signal transduction pathways, possibly involving protein kinase C, during liver tumour promotion.

Reduced level of serum cholesterol in low protein-fed wistar rats administered gossypol and chloroquine

Gossypol and chloroquine were administered in goya oil and distilled water, respectively, to low protein-fed (LP) and normal protein-fed (NP, control) adult male albino Wistar rats for 4 and 8 weeks' duration. Gossypol (GP) and chloroquine (CQ) were administered separately and in combination (GPCQ). At the end of the treatment periods, the rats were anesthetized and blood drawn by cardiac puncture, centrifuged, and sera obtained for assay of total cholesterol and triglycerides levels. The data obtained were analyzed by two-way ANOVA. The results showed that the interaction of GP and CQ in LP and NP-fed rats produced significant effects (P<0.001) on the serum levels of cholesterol and triglycerides. Serum cholesterol level was lower at 8 than at 4 weeks in LP-fed rats but higher at 8 than at 4 weeks in NP-fed rats. The administration of GP, CQ, and GPCQ resulted in lower serum cholesterol and triglycerides at 8 than at 4 weeks in LP fed rats but higher serum cholesterol at 4 than at 8 weeks in NP-fed rats. In LP and NP-fed rats, the levels of serum cholesterol and triglcerides were generally lower in GCPQ-treated than GP- or CQ-treated rats. The implications of the findings are discussed.

Protein increases glomerular eicosanoid production and activity of related enzymes

We examined the in vitro production of PGE2, 6-keto PGF1 alpha and TxB2 by isolated glomeruli from rats fed a low (6% casein) or a high (40% casein) protein diet for approximately eight weeks. Glomeruli from high protein-fed rats produced significantly greater amounts of PGE2, 6-keto PGF1 alpha and TxB2 under basal conditions and in response to the addition of 100 nM angiotensin II (Ang II) than glomeruli from low protein-fed rats. To elucidate the mechanisms by which greater protein intake enhanced the glomerular production of eicosanoids, we explored phospholipase (A2 and C) and cyclooxygenase activity in glomeruli isolated from low- or high-protein fed rats. PE-specific PLA2 activities were significantly increased in glomeruli from rats fed a high protein diet when compared to a low protein diet. On the other hand, PC-specific PLA2 activities were significantly decreased in glomeruli from rats fed a high protein diet. No significant difference in PIP2-PLC activities was detected between glomeruli of the two dietary groups. The cyclooxygenase content and activity was significantly greater in glomeruli from rats fed a high protein diet than in glomeruli from rats fed a low protein diet. Glomeruli of rats fed a 50/50 mixture of the diets (23% casein) had amounts and activity of cyclooxygenase and activities of PE-specific PLA2 intermediate between those of high and low protein-fed animals. In conclusion, increased synthesis of eicosanoids by glomeruli from rats fed a high protein diet may be mediated by increases in the amount and activity of cyclooxygenase coupled with enhanced activity of PE-specific PLA2.

Effect of Environmental Enrichment during Nutritional Rehabilitation on Body Growth, Blood Parameters and Cerebral Cortical Development of Rats

Environmental enrichment has been reported to aid recovery from behavioral deficits associated with malnutrition in infants and young rats. This study investigated whether corresponding neuroanatomical changes could be detected. Rats were suckled either by well-fed dams or dams malnourished during lactation. At weaning, well-fed males were either housed in pairs (standard condition, SC) or 12 per large cage with toys (enriched condition, EC) and fed a 17% protein diet (SC control and EC control, respectively). Malnourished pups were fed either a 17% (rehabilitation; "rehab") or a 6% (low protein) protein diet and housed in the SC or EC environment (SC rehab, EC rehab, SC low protein, and EC low protein). After 30 d there were no differences in hematocrit, serum total protein and albumin levels between SC and EC animals. Rehab rats had significantly lower serum total protein and albumin levels than did controls. Cortical thickness and dendritic branching of occipital cortex pyramidal cells were evaluated. Early malnutrition did not permanently affect cortical thickness. EC rehab rats had thicker cortices than did SC rehab rats at almost all locations measured. SC rehab rats had fewer high order dendrites than did SC controls. The difference in dendritic branching between EC and SC rats was 44% among rehab rats, 21% among controls and 11% (not significant) among low protein-fed rats. Environmental enrichment during nutritional rehabilitation enhances dendritic branching and thickness of the occipital cortex.

Effect of Environmental Temperature on Energy Balance and Thermogenesis in Rats Fed Normal or Low Protein Diets

Rats fed a low protein (9% metabolizable energy) diet and house at 24°C gained less weight and body energy then controls fed a normal (25%) protein diet. Energy intake and expenditure corrected for body size (kJ/(kg0.75·d)] were similar in rats fed the two diets, but energetic efficiency was suppressed in low protein-fed rats, and the thermogenic response to norepinephrine and the activity of brown adipose tissue (mitochondrial GDP binding) were both significantly elevated. Housing at a higher temperature (29°C) suppressed energy expenditure and brown fat activity in animals fed either diet, and gross efficiency was greater in control animals at 29°C than at 24°C but unaffected in the protein-deficient group. The differences in brown fat activity between dietary groups were still apparent at 29°C. The results suggest that thermogenesis induced by feeding low protein diets is not markedly inhibited by a higher environmental temperature.

DECREASED SERUM SOMATOMEDIN-C (Sm-C) RESPONSE TO GROWTH HORMONE (GH) IN HYPOPHYSECTOMIZED RATS FED A LOW PROTEIN DIET: EVIDENCE FOR A POSTRECEPTOR DEFECT

Reduced number of liver GH receptors may participate to the fall of Sm-C in fasted and protein restricted rats. However, a possible role for a postreceptor defect has not been evaluated. To address this question, the liver GH binding sites and the serum Sm-C responses to single injections of saline or bovine GH (0.25; 0.5; 1 and 5 mg/rat; 5 rats/dose) were determined in hypophysectomized female rats, submitted for 7 days to a normal (15 %; n = 25) or a low protein diet (5 %; n = 25). Binding studies were performed with 125I-bovine GH. The liver GH binding capacities (pmol/mg DNA; mean ± SE) of the low protein-fed rats (0.85 ± 0.07) were not significantly different (P > 0.05) from those of normal protein-fed animals (1.09 ± 0.16). Also, the affinity constants were not affected by protein intake. Basal serum Sm-C levels, determined by RIA, were similar in both groups and increased in a dose-dependent manner in response to GH. However for each GH dose, the Sm-C response in the low protein-fed rats was lower. The maximal Sm-C response to GH (5 mg) was in the malnourished rats (0.13 ± 0.04 U/ml) significantly reduced when compared to the controls (0.36 ± 0.03 U/ml; P< 0.001).In conclusion, the blunted maximal Sm-C response to GH together with unaltered liver GH binding suggest that protein malnutrition induces a GH postreceptor defect.

Dietary protein intake conditions the degree of renal vasoconstriction in acute renal failure caused by ureteral obstruction

Whole kidney inulin (CIn) and PAH (CPAH) clearances were measured after unilateral release of bilateral ureteral obstruction (BUO) of 24-h duration in rats fed for 4 wk isocaloric diets containing either 40% casein (high protein diet) or 6% casein (low protein diet). Values for CIn and CPAH were markedly depressed in both groups but to a greater extent in high protein-fed rats, averaging less than 60% of values measured in low protein-fed animals. Captopril, an inhibitor of the angiotensin I converting enzyme, increased CIn and CPAH markedly but comparably in high or low protein fed rats. Micropuncture studies performed after unilateral release of BUO in another group of rats fed a high or a low protein diet revealed lower levels of glomerular plasma flow rate (QA) and single nephron glomerular filtration rate (SNGFR) in rats fed a high protein diet. Values for renal arteriolar resistances were nearly twofold in high as compared with low protein-fed animals. Infusion of OKY-1581, an inhibitor of thromboxane A2 synthetase, increased both QA and SNGFR, decreased arteriolar resistances, and increased glomerular capillary ultrafiltration coefficient in high but not in low protein-fed rats. Urinary thromboxane B2 excretion per milliliter of GFR was greater in rats fed a high protein diet than in those fed a low protein diet after release of BUO but not in normal rats. In normal rats infusion of OKY-1581 did not increase CIn or CPAH.(ABSTRACT TRUNCATED AT 250 WORDS)

Influence of Diet Composition on Serum Triiodothyronine (T3) Concentration, Hepatic Mitochondrial Metabolism and Shuttle System Activity in Rats

Two experiments were conducted to determine if variations in diet composition sufficient to alter circulating triiodothyronine (T3) concentration would influence hepatic mitochondrial metabolism. In experiment I, mitochondrial respiration and the activity of succinate dehydrogenase (SDH), cytochrome oxidase (CO) and α glycerophosphate dehydrogenase (mα-GPD) were measured in 42-day-old male rats fed diets containing casein/carbohydrate/fat: 8/73/10% (low protein), 22/59/10% (control protein), and 45/36/10% (high protein) for 3 weeks. When compared to control, serum T3 was increased 2–3 times in the low and decreased 19% in the high protein-fed groups. Mitochondria isolated from low protein-fed rats consumed less oxygen in both state 4 and state 3 with succinate as substrate when compared to control or high protein fed rats. However, ADP/O and respiratory control (RC) ratios were similar in all groups. Activity of SDH and CO was decreased only in low protein-fed rats. Mα-GPD activity was increased in the low and decreased in the high protein fed-rats. In experiment 2, α-glycerophosphate shuttle activity was increased 2–3 fold and malate-aspartate shuttle activity decreased 60% in intact mitochondria isolated from low protein-fed rats when compared to rats pair-fed control diet. These results suggest a role for diet composition as a regulator of hepatic intermediary metabolism mediated by thyroid hormones.dietary protein mitochondrial metabolism triiodothyronine

Effects of nephron reduction and dietary protein content on renal ammoniagenesis in the rat

Urinary ammonium excretion, in vitro ammoniagenesis and the activities of renal cortical phosphate-dependent glutaminase (PDG) and glutamic dehydrogenase (GLDH) were measured in rats with a reduced renal mass. Following contralateral nephrectomy, ammonium excretion per nephron, ammonia production and the activities of PDG and GLDH were all increased significantly in remnant kidneys of rats fed high protein diets. In rats fed low protein diets, although PDG activity increased, GLDH activity and ammonia production and excretion did not increase in remnant kidneys following contralateral nephrectomy. Ammonia production and excretion were greater in rats fed high than low protein diets, a difference that was corrected by the addition of mineral acid to the diets of low protein-fed rats. Acid supplementation to the low protein group did not result in enhanced ammonia production or GLDH activity following a reduction in renal mass. The data indicate that the increased rate of ammoniagenesis which occurs following nephron reduction is markedly influenced by dietary protein content. A lack of enhanced GLDH activity may underlie the lack of increased ammonia production of low protein-fed rats following nephron reduction.