ABSTRACT
The study was conducted in mice in order to elucidate whether psycho-social stimulation produced in an interconnecting box system was able to induce alterations in some circulating lipid fractions and in heart lipoprotein lipase (LPL) activity. Two groups of male mice were studied: A--a group isolated in glass jars from weaning to the age of 12-13 weeks and then transferred to the interconnecting box system with a reduced number of female mice, to 26 weeks of age; B--a second group isolated from weaning to 26 weeks of age, as an extremely opposite situation to group A. Control mice were kept in standard cages from weaning to the end of the experiment. Total cholesterol and triglycerides were determined in blood plasma, and heart LPL activity was determined in small portions of the ventricles. Cholesterol decreased significantly in group A (p less than 0.002) and in group B (p less than 0.05) vs. controls. No alterations were observed either in plasma triglycerides or in LPL activity in either of the two groups.
Subject(s)
Lipids/blood , Lipoprotein Lipase/metabolism , Myocardium/enzymology , Social Environment , Stress, Psychological/enzymology , Animals , Cholesterol/blood , Humans , Male , Mice , Social Isolation , Triglycerides/bloodABSTRACT
The influence of hypothalamic electric stimulation and administration of 6-hydroxydopamine (6-OHDA) on cardiac lipoprotein lipase (LPL) activity was investigated in 19 rabbits either acutely stimulated in the hypothalamic ventro-medial nucleus (HVMN), or injected with 6-OHDA, or submitted to both experimental procedures. 6 animals served as controls. In rabbits pretreated with 6-OHDA a significant decrease of LPL activity was found with respect to controls (p less than 0.005) and also to stimulated animals (p less than 0.005). The possible mechanism underlying this change is discussed.
Subject(s)
Electric Stimulation , Hydroxydopamines/pharmacology , Hypothalamus, Middle/physiology , Lipoprotein Lipase/metabolism , Myocardium/enzymology , Animals , Female , Heart/drug effects , Heart/physiology , Male , Oxidopamine , RabbitsABSTRACT
Changes in heart lipoprotein lipase (LPL) activity provoked by colchicine (0.5 mg/100 g body weight) and heparin (10 IU/100 g body weight) were studied in heart homogenates and serum from rats treated with both drugs or with heparin alone. In addition experiments were carried out in vitro in which the action of colchicine alone and colchicine plus heparin was compared with controls. In vivo experiments showed that colchicine decreased post-heparin release of the enzyme in fed animals, but was incapable of doing so in fasted animals. Accordingly, heart LPL activity, expressed in percentage of control values, did not change in fed animals, but significantly decreased (p less than 0.05) in fasted animals. In the in vitro experiments, colchicine significantly decreased heart LPL activity (p = 0.025) whether or not heparin was present and regardless of the nutritional state of the rats. Apparently, colchicine has two distinct actions on heart LPL activity: a direct one on the enzyme and another mediated by the nutritional state of the animal.
Subject(s)
Colchicine/pharmacology , Lipoprotein Lipase/metabolism , Myocardium/enzymology , Animals , Fasting , Heparin/pharmacology , In Vitro Techniques , Male , RatsABSTRACT
Se propone un método relativamente económico y de equipamiento sencillo, para la determinación de actividad de lipasa lipoproteínica en corazón y tejido adiposo epididimal de rata. Este método emplea intralipid como substrato artificial, albúmina bovina fracción V, suero de caballo y solución amortiguadora CINH4/NH4OH 0,1M, pH 8,6 en el medio de incubación. El análisis de varianza de la regresión indica buena linealidad cuando se compara actividad enzimática vs. tiempos de ambos tejidos (p<0,01), actividad enzimática vs. cantidad de tejido adiposo (como medida de la concentración de enzima en el homogeneizado) (p<0,01), actividad vs. cantidad de tejido cardíaco (p<0,05). La inhibición de la actividad por CINa y sulfato de protamina (1M y Lmg/ml en el medio de incubación, respectivamente), mostró resultados estadísticamente significativos (p=0,025), demostrando la especialidad del método(AU)
Subject(s)
Animals , Male , Rats , Lipoprotein Lipase/metabolism , Epididymis/enzymology , Adipose Tissue/enzymology , Myocardium/enzymologyABSTRACT
Possible enhancement by free fatty acids (FFA) of the arrhythmogenic actions of ouabain was studied in rabbits. The mean dose of ouabain required for inducing ventricular tachycardia or fibrillation in conscious animals was significantly lowered by intravenous injection of 5 ml of a 20% fat emulsion (Lipofundin), which significantly elevated circulating FFA. Lipofundin alone did not initiate arrhythmias in another group of animals. The transmembrane action potential duration (APD) and the maximum rate of depolarization (Vmax)recorded from rabbit papillary muscles were markedly reduced under the influence of 2 mM octanoate, a short-chain FFA. Ouabain, 10(-7M), reduced significantly only the APD measured at zero level of repolarization. In papillary muscles exposed to both octanoate and ouabain, resting potential, overshoot, APD, and Vmax were all significantly decreased below control values. The synergistic arrhythmogenic actions of FFA and ouabain might be explained by the inhibiting effect of both agents on membrane (Na+ + K+)ATPase.
