ABSTRACT
The aim of this study was to measure the nutrient oxidation rate during walking at different speeds and to identify the walking speed associated with the highest fat oxidation rate in a group of prepubertal boys with different levels of adiposity. Twenty-four prepubertal boys (age, 10 +/- 1 yr) with different levels of overweight (body mass index, 25.5 +/- 3.5 kg/m(2); sd score of body mass index, 3.4 +/- 1.1) performed a treadmill test. We measured by indirect calorimetry their respiratory exchange while they walked at speeds of 4, 5, and 6 km/h as well as their maximal oxygen uptake. The fat oxidation rate did not change significantly when the speed of walking was increased, whereas carbohydrate oxidation increased significantly (P < 0.001). A significant (P < 0.05) association was found between adiposity (percent fat mass) and the fat to carbohydrate oxidation ratio during walking at 4, 5, and 6 km/h (r = 0.37, r = 0.37, and r = 0.36, respectively), adjusting for exercise intensity (maximal oxygen uptake, percentage). The lowest fat to carbohydrate oxidation ratio, i.e. the highest fat oxidation/carbohydrate oxidation rate, was found at a walking speed of 4 km/h. Moderately intense exercise promoted the highest fat to carbohydrate oxidation ratio. Increasing the exercise intensity did not promote fat oxidation. Therefore, walking at a speed of 4 km/h is recommended as practicable exercise for obese boys and, consequently, for the treatment of childhood obesity.
Subject(s)
Dietary Carbohydrates/metabolism , Dietary Fats/metabolism , Exercise , Obesity/metabolism , Adipose Tissue/metabolism , Child , Energy Metabolism , Humans , Male , Obesity/therapy , Oxidation-Reduction , Oxygen Consumption , Puberty , WalkingABSTRACT
The pharmacodynamic features of the new nonpeptide kinin B2 receptor antagonist FR 173657 were evaluated on pig, rabbit, guinea pig, and human native kinin B2 receptors. FR 173657 exerted high antagonistic activity in all preparations examined. In particular, it acts as a competitive antagonist in the rabbit jugular vein (pA2 8.9) and in the human umbilical vein (pA2 8.2) but as a noncompetitive antagonist in the pig coronary artery (pKB 9.2) and in the guinea pig ileum (pKB 9.2) stimulated with the selective B2 receptor agonist bradykinin (BK). In contrast, FR 173657 failed to antagonize the biological effects of the selective B1 receptor agonist LysdesArg9BK in the pig renal vein, rabbit aorta, and human umbilical vein, three kinin B1 receptor systems. Moreover, this compound was inactive against the effects induced by noradrenaline, 5-hydroxytryptamine, endothelin-1, angiotensin II, substance P, acetylcholine, and histamine in the B2 receptor preparations. Taken together, these results demonstrate that FR 173657 is the first potent nonpeptide B2 receptor antagonist with high affinity, selectivity, and specificity for kinin B2 receptors of different species, including man.
Subject(s)
Quinolines/pharmacology , Receptors, Neurokinin-3/antagonists & inhibitors , Adult , Animals , Binding, Competitive , Coronary Vessels/drug effects , Coronary Vessels/ultrastructure , Female , Guinea Pigs , Humans , Ileum/drug effects , Ileum/ultrastructure , In Vitro Techniques , Jugular Veins/drug effects , Jugular Veins/ultrastructure , Male , Rabbits , Species Specificity , SwineABSTRACT
The aim of the present study was to characterize pharmacologically endothelin receptors that are present in human umbilical vessels. 2. Endothelin-1 (ET-1) and endothelin-2 (ET-2) are potent stimulants of both the human umbilical artery (pEC50 7.9 and 7.5) and vein (pEC50 8.1 and 8.0). Endothelin-3 (ET-3) is inactive on the artery but contracts the vein (pEC50 7.6). IRL1620 is inactive in both vessels. The order of potency of agonists is suggestive of a typical ET(A) receptor in the artery (ET-1 = ET-2 > > ET-3) and a mixture of ET(A) and ET(B) receptors in the vein (ET-1 = ET-2 > or = ET-3). 3. The selective ET(A) receptor antagonist, BQ123, competitively inhibits the effect of ET-1 in the human umbilical artery (pA2 6.9), while in the vein, only a mixture of BQ123 and BQ788 (a selective ET(B) antagonist) weakly displaces to the right of the cumulative concentration-response curve to ET-1. Contractions induced by ET-3 in the vein are inhibited by BQ788 (pA2 7.6), but not by BQ123. 4. Inhibition of Ca2+ channels by nifedipine (0.1 microM) is accompanied by a significant decrease of the maximal response to ET-1 by 40% in the artery and by 30% in the vein. The response of the vein to ET-3 is almost abolished by nifedipine. 5. The results indicate that: (i) endothelins contract the human isolated umbilical artery via stimulation of an ET(A) receptor type; (ii) the contraction induced by ET-1 in the vein is mediated by both ET(A) and ET(B) receptors, while ET-3 stimulates the ET(B) receptor; (iii) the contribution of Ca2+ channels to the contraction mediated by the ET(B) receptor appears to be more important than to that mediated by the ET(A) receptor.
Subject(s)
Receptors, Endothelin/drug effects , Umbilical Arteries/drug effects , Umbilical Veins/drug effects , Adult , Binding, Competitive/drug effects , Calcium Channel Blockers/pharmacology , Endothelin Receptor Antagonists , Endothelin-1/metabolism , Endothelin-1/pharmacology , Endothelin-2/metabolism , Endothelin-2/pharmacology , Female , Humans , In Vitro Techniques , Muscle Contraction/drug effects , Muscle, Smooth, Vascular/drug effects , Nifedipine/pharmacology , Peptides, Cyclic/pharmacology , Pregnancy , Receptors, Endothelin/agonistsABSTRACT
The newly discovered neuropeptide, nociceptin (alias orphanin FQ), was tested for its potential direct effects, as well as for its ability to modify the electrically evoked contractions in several isolated organs suspended in vitro. The electrically stimulated mouse vas deferens is a sensitive preparation on which nociceptin exerts an inhibitory effect which is not affected by naloxone. The mouse vas deferens is therefore proposed as a bioassay for nociceptin and related compounds.