Use of the weight of various organs and tissues together with their specific metabolic activity for prediction of basal metabolism (BM) seems to be promising. In this study we compared the use of this method with those based on simple or multiple regression analyses. We observed that 97.4% of differences in BM in a group of nine adult male Wistar rats weighing 273--517 g could be accounted for by changes in tissue and organ weights. BM measured in lean Zucker and Sprague-Dawley rats did not diverge from the prediction of the model by >1.6%. According to the organ-based model as well as multiple regression analyses, but not simple regression analyses, BM was increased 18--21% in young rats, decreased 6--7% in food restricted/refed rats, and decreased 19--21% in aged rats. Only with obese rats did the predictions of the two methods diverge. The main reason for this discrepancy seems to be the way adipose tissue size and metabolism are taken into account.

We examined the effects of feeding conjugated linoleic acids (CLA) to adult male hamsters on several components of energy metabolism and body composition. Hamsters (n = 54) were assigned for 6-8 wk to one of three diets: 1) a standard diet (in percentage energy: lipids, 33, carbohydrates, 49, and proteins, 18); 2) to the standard diet augmented with the 9c,11t-isomer of CLA to 1.6% of energy (R group); or 3) the standard diet augmented with the 9c,11t-isomer and the 10t,12c-CLA isomer to 3.2 (1.6 + 1.6) % of energy (CLA mix group). (15)N uniformly labeled milk-protein was included in the diet to measure the incorporation of dietary protein into liver and muscle. Basal metabolic rate, thermogenic response to feeding and energy expenditure during spontaneous activity or during an exercise at approximately 60% of VO(2max) were measured. Carnitine palmitoyltransferase-I (CPT-I), leptin, insulin and triiodothyronine concentrations, as well as the in vivo overall adiposity changes were also determined. After 6 wk, the whole-body triglyceride content determined in vivo by NMR was significantly higher in the R group than in the control and CLA mix groups. The CLA mix group differed from the others in the lack of body triglyceride accumulation between d 21 and d 45 of the study, and the appearance of a slight insulin-resistance (homeostatic model assessment index, P < 0.05). Paradoxically, the lack of effect on whole-body lipid oxidation was associated with a greater CPT-I-specific activity in tissues of both CLA-fed groups (P < 0.05). No other major effects of CLA feeding were detected. In conclusion, CLA supplementation in hamsters did not affect adipose weight or the components of energy expenditure despite a theoretically higher capacity of red muscle to oxidize lipids. Only a CLA mixture prevented whole-body triglyceride accumulation over time.

Binding of [125I] Tyr A14 human insulin ([125I] insulin) was measured at 4 degrees C in glomeruli and pieces of tubule microdissected from collagenase-treated rat kidneys. For glomeruli and all segments tested, total and non specific binding increased linearly with glomeruli number or tubular length. When determined with 4.0 nM labelled hormone, the distribution of specific binding sites (expressed as 10(-18) mol [125I] insulin bound per glomerulus or mm tubule length) was as follows: glomerulus, 2.5 +/- 0.3; proximal convoluted tubule (PCT), 12.6 +/- 0.6; pars recta (PR), 4.0 +/- 2.6; thin descending limb (TDL), 0.6 +/- 0.2; thin ascending limb (TAL), 0.6 +/- 0.2; medullary thick ascending limb (MAL), 0.8 +/- 0.1; cortical ascending limb (CAL), 2.1 +/- 0.1; distal convoluted tubule (DCT), 5.6 +/- 1.1; cortical collecting tubule (CCT), 3.2 +/- 0.3 and outer medullary collecting tubule (MCT), 2.3 +/- 0.1. Specific [125I] insulin binding to glomeruli and tubule segments was time and dose-dependent, saturable, reversible after elimination of free labelled ligand, and inhibited by unlabelled human insulin. When analysed in Scatchard and Hill coordinates, the binding data revealed a negative cooperation in the interaction processes between [125I] insulin and glomerular and tubular binding sites, with apparent dissociation constants and Hill coefficients of the following values: glomerulus, 0.6 nM and 0.60; PCT, 10.0 nM and 0.55; MAL, 4.3 nM and 0.80; CAL, 2.0 nM and 0.74; CCT, 7.6 nM and 0.80 and MCT, 1.0 nM and 0.57 respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

In obese rats, basal metabolism and postprandial lipid oxidation increased during butter feeding, which appeared to prevent fat accumulation in the long term. In lean rats, butter feeding favored lipid utilization by working muscles, an observation that deserves further investigation in terms of endurance and performance.

The composition of the preexercise food intake is known to affect substrate utilization during exercise and thus can affect long-term changes in body weight and composition. These parameters were measured in male rats exercised 2 h daily over 5 wk, either in the fasting state or 1 h after they ingested a meal enriched with glucose (Glc), whole milk protein (WMP), or alpha-lactalbumin-enriched whey protein (CPalphaL). Compared with fasting, the Glc meal increased glucose oxidation and decreased lipid oxidation during and after exercise. In contrast, the WMP and CPalphaL meals preserved lipid oxidation and increased protein oxidation, the CPalphaL meal increasing protein oxidation more than the WMP meal. At the end of the study, body weight was larger in the WMP-, Glc-, and CPalphaL-fed rats than in the fasted ones. This resulted from an increased fat mass in the WMP and Glc rats and to an increased lean body mass, particularly muscles, in the CPalphaL rats. We conclude that the potential of the CPalphaL meal to preserve lipid oxidation and to rapidly deliver amino acids for use during exercise improved the efficiency of exercise training to decrease adiposity.

Angiotensin I converting enzyme (ACE) and kininase activities were measured in various segments of the rabbit nephron. ACE was determined with tritiated hippuryl-glycylglycine as substrate. Lysyl-bradykinin (LBK) hydrolysis (kininase activity) was measured by radioimmunoassay. ACE was only found in the glomerulus and in the two parts of proximal tubule: the convoluted proximal tubule and the pars recta (PR). It was distributed along a concentration gradient which increased from the glomerulus to PR. Kininase activity was found in both proximal and distal parts of the nephron. Besides intense LBK-hydrolyzing activity in the proximal tubule, a kininase activity was also found in the medullary collecting tubule (MCT). Kininase activity in the glomerulus and the proximal tubule was completely inhibited by chelating agents. Captopril inhibited this activity only in the PR and at high concentrations (above 10(-7) M). These results indicate that several types of enzymes other than ACE hydrolyze kinins in the glomerulus and in the proximal tubule. The contribution of ACE to kinin hydrolysis appears only minimal. The kininase activity found in MCT was different from ACE and other proximal tubule kininases because it was not inhibited by chelating agents. This kininase may play a physiological role in inactivating the kinins formed by kallikrein at or beyond the connecting tubule.

Portha. Energy restriction with protein restriction increases basal metabolism and meal-induced thermogenesis in rats. Am J Physiol Regul Integr Comp Physiol 284: R751-R759, 2003. First published November 27, 2002 10.1152/ajpregu.00268.2002We previously observed an increased sympathetic nervous system (SNS) activity that was partly responsible for a defect in the insulin secretion response to glucose after postweaning protein-energy restriction (PER) in female rats. These results, together with other data on low-protein feeding, suggested that a low protein-toenergy ratio (P/E) in the diet could stimulate energy expenditure (EE), but direct measurements of EE have never been reported under conditions of PER. The goal of the present study was thus to quantify the changes induced by PER to body composition, the various parameters of EE, and plasma triiodothyronine levels. PER induced severe growth retardation, but the subcutaneous white and interscapular brown adipose tissue masses were preserved. Basal metabolism, meal-induced thermogenesis, and triiodothyronine levels were increased, but substrate utilization by the working muscles was unaffected. Meal-induced thermogenesis was increased by spontaneous activity in PER rats only. These results suggest that rats adapt to a low P/E in the diet by burning part of their excess nonprotein energy and storing the remaining excess in subcutaneous adipose tissue. malnutrition; brown adipose tissue; white adipose tissue; indirect calorimetry; triiodothyronine; spontaneous activity SYMPATHETIC NERVOUS SYSTEM (SNS) activity and/or the utilization of ingested energy are unchanged or moderately decreased by calorie restriction without protein restriction (12,14,16,25), but increased SNS activity has repeatedly been reported in rats fed a low-protein diet, as evidenced by elevated norepinephrine turnover in the heart and urinary norepinephrine excretion. This increased SNS activity, observed in both young and adult animals, was shown to induce an increase in interscapular brown adipose tissue (IBAT) mass and activity and sometimes in thermogenesis (26,27,34). Therefore, a low protein-to-energy ratio (P/E) in the diet was proposed as an explanation for the above disturbances in SNS activity and in the utilization of the ingested energy in response to a low-protein diet (26). During a recent study concerning the impact of postweaning protein-energy restriction (65% of normal ad libitum daily food intake, with a 5% protein diet) on glucose metabolism, we noted a considerable stimulation of SNS activity that was shown to be partly responsible for reduced glucose-stimulated insulin secretion and resistance of the hepatic glucose production pathway to insulin action (19, 24). These two phenomena were not observed when subjecting rats to energy restriction alone (65% of normal ad libitum daily food intake, with a 15% protein diet) (24). Thus these data also suggest that the impact of protein-energy restriction on SNS activity and metabolism may mainly be due to a low P/E in the diet...

Vasopressin receptors in distal segments of the rat nephron were identified in isolated tubules using two labeled ligands: the [1-(beta-mercapto-beta,beta-cyclopentamethylenepropionic acid), 2-(O-methyl)tyrosine,4-threonine,8-ornithine,9-125I-tyrosylamide]- vasotocin [125I-d(CH2)5[Tyr(Me)2,Thr4,Tyr-NH2(9)]OVT] and the linear analogue, Phaa1,D-Tyr(Me)2,Phe3,Gln4,Asn5,Arg6, Pro7,Arg8,125I-Tyr-NH2(9) [125I-Tyr-NH2(9)-linear antagonist (LA)-V1a)]. Specific 125I-d(CH2)5[Tyr(Me)2,Thr4,Tyr-NH2(9)]-OVT binding to cortical collecting ducts (CCD) was saturable with incubation time and dose, reversible after elimination of free ligand, and characterized by the following rank order for recognition of vasopressin analogues: desGly9-d-(CH2)5-[Tyr(Et)2,Val4]arginine vasopressin (AVP) greater than or equal to d(CH2)5[Tyr-(ET)2,Val4]AVP greater than or equal to AVP greater than or equal to d(CH2)5[Tyr(Me)2]AVP = 1-desamino-8-D-arginine vasopressin (DDAVP) greater than or equal to Tyr-NH2(9)-LA-V1a greater than [8-arginine]vasotocin (AVT) greater than d(CH2)5[Tyr(Me)2, Thr4,Tyr-NH2(9)]OVT greater than oxytocin (OT) greater than [Phe2,Orn8]VT much greater than [Thr4,Gly7]-OT. Scatchard plots of dose-dependent 125I-Tyr-NH2(9)-LA-V1a binding to medullary thick ascending limbs (MTAL), CCD, and outer medullary collecting ducts (OMCD) revealed the presence of high- and low-affinity binding sites corresponding to V1a and V2 vasopressin receptors, respectively; the densities of V1a receptors are approximately 20% of the total number of vasopressin receptors in CCD and 5% in MTAL and OMCD.