Charlotte R. Hollett

Localization and characterization of a lipase in rat adipose tissue

A lipolytic enzyme from rat adipose tissue has been studied in a cell-free system. Most of the activity toward triglyceride was recovered in a fraction that sedimented at 105,000 g for 18 hours. Properties of the high-speed sediment included: (a) a strong pH dependency, with optimum activity at pH 7.4; (b) instability, half-life of 2 1/2–3 days; (c) partially inactivated by heat; (d) activated by SH reagents; (e) stimulation by epinephrine was observed only in a preparation which had become partially or totally inactivated during storage; (f) neither the whole homogenate nor the fully active fractions were stimulated by epinephrine.

An inhibitor of the lipolytic reaction from post-heparin plasma of normal dogs

Abstract A factor which was capable of inhibiting the hpolytic activity in vitro of the heparin-induced clearing factor lipase has been isolated from normal post-heparin plasma. Inhibition was found to be proportional to the concentration of the inhibitor and to the time during which the inhibitor was present in the reaction medium. Increased concentrations of substrate or enzyme did not alter the magnitude of inhibition. The action of the inhibitor appears to be of the non-competitive type.

Tissue lipases and the postheparin plasma clearing factor

Abstract Parallel experiments with purified clearing factor of postheparin plasma and acetone powder extracts of rat heart and adipose tissue indicated that these are not identical enzyme systems. Serum and heparin stimulated the tissue lipases but inhibited the clearing factor. The inhibition by sodium pyrophosphate and protamine sulfate of the tissue lipases was reversed, or partially reversed, by heparin, but clearing factor was further inhibited. Extracts of frozen pulverized adipose tissue did not require serum for activity, whereas extracts of acetone powders of heart and adipose tissue showed little activity in the absence of serum. It is suggested that the means of enzyme preparation may modify the lipolytic response.

Some properties of a lipid mobilizing substance from the calf mid-brain

Abstract 1. 1. A substance with lipid mobilizing properties has been isolated from the calf mid-brain. 2. 2. The lipid mobilizing factor was chromatographically, electrophoretically and spectroscopically similar to hypoxanthine, but differed from the purine in solubility and in lipolytic properties. 3. 3. The incubation medium retained lipid mobilizing properties following tissue exposure, and the tissue retained some lipolytic activity after exposure to the lipid mobilizing factor. 4. 4. A parallelism existed between the relationship of the mid-brain lipid mobilizing factor and adrenergic blocking agents, and epinephrine and adrenergic blocking agents with respect to lipid mobilization. 5. 5. An inhibitor of lipid mobilization also was present in the crude mid-brain extract. The inhibitor, after separation from the lipid mobilizing component, suppressed the lipolytic activities of the purified mid-brain extract and the catecholamines (epinephrine and norepinephrine).

A lipid mobilizing substance from the calf mid-brain

Abstract Many naturally occurring substances stimulate the mammalian fat cell to convert stored triglycerides into fatty acids and glycerol, which are transported to other organs. These adipokinetic, or lipid mobilizing, substances are thought to stimulate a lipolytic enzyme within the fat cell. Such substances include at least seven pituitary hormones (Rudman, et al 1965) , the catecholamines (Rudman, et al 1965) and a number of peptides which are related, either directly or indirectly, to the pituitary gland (Chalmers et al 1960 , Rudman et al 1962) . Lipid mobilizing activity has been found in extracts of the hypothalamus and of the posterior pituitary of cadavers (Kadas and Nagy 1965) . This report describes the isolation and properties of a lipid mobilizing factor (LMF) from the calf mid-brain. Since the hypothalamus and certain other areas of the mid-brain are particularly rich in norepinephrine (1966), comparative studies of the catecholamines and the mid-brain extract were performed. Evidence is presented to show that the LMF from the mid-brain is not a catecholamine.

Tentative identification of a lipid mobilizing substance from the calf mid-brain

Abstract An earlier report described the isolation and some properties of a lipid mobilizing factor (LMF) from the calf mid-brain, (1968). This factor has been tentatively identified as a hypoxanthine-like compound. LMF was indistinguishable from the purine base, hypoxanthine by paper electrophoretic and paper chromatographic techniques, and in u.v. absorption spectra.

Inhibitor of catecholamine-induced free fatty acid mobilization from the calf midbrain

Abstract A substance which inhibits free fatty acid (FFA) mobilization has been isolated from the calf midbrain. The inhibitor suppressed norepinephrine-induced FFA mobilization in adipose tissue slices, and the isolated fat cell preparation: theophylline-stimulated lipolysis in adipose tissue also was inhibited. Simultaneous infusion of norepinephrine and inhibitor in the dog suppressed FFA mobilization and the rise in blood pressure associated with norepinephrine. The inhibitor action on FFA mobilization and on blood pressure was reversible. A parallelism existed between the time of exposure to the inhibitor and the extent of inhibition. Addition of inhibitor at varying time intervals during norepinephrine induced FFA release revealed that inhibition could occur at any time during the mobilization process. A procedure is presented for the purification of the midbrain inhibitor. Some properties of the purified preparation are discussed.

Identification and structural characterization of an inhibitor of catecholamine-induced free fatty acid mobilization from the calf midbrain

Abstract A substance which inhibits norepinephrine-induced free fatty acid mobilization has been isolated from the calf midbrain. A preparation of the inhibitor, considered to be highly purified, was resolved into two distinct components by paper chromatography. Both components (designated Fractions I and II) inhibited free fatty acid mobilization in adipose tissue fragments in the presence of norepinephrine. One component (Fraction II) was identical chromatographically to an inhibitor of free fatty acid mobilization prepared from the dog hypothalamus. Fraction II has a molecular weight of 136, and appears to have the structure of a pyridylacetic acid.

Lipolytic activity and plasma-free fatty acid levels following the administration of an inhibitor of the clearing reaction

Abstract An inhibitor of the heparin-induced lipemia clearing factor has been isolated from dog post-heparin plasma. The purified inhibitor (950-fold) when injected into rats before heparin administration resulted in a marked diminution of the clearing factor release as determined by the ability of the post-inhibitor-heparin plasma to hydrolyse a triglyceride emulsion in vitro; the inhibitor also suppressed lipolysis in vivo or the rise in plasma free fatty acids that follows heparin administration. When the inhibitor injection followed that of heparin, the lipolytic activity in vitro of the post-heparininhibitor plasma did not differ from that of post-heparin plasma no marked change was seen in plasma free fatty acid levels. The inhibitor appeared to prevent the release of the clearing factor if the animal were pre-treated with the inhibitor before heparin was administered; however, if clearing factor were already in the circulation at the time the inhibitor was given no effect on lipolysis in vivo or in vitro was evident.

The effect of a bovine hypothalamic factor on mouse brain neurotransmitters.

Abstract A substance isolated from the bovine hypothalamus was found to protect against the toxicity of amphetamine in the crowded mice situation. We measured the levels of brain catecholamines (norepinephrine and dopamine) and γ-aminobutyric acid during crowding following the administration of amphetamine, hypothalamic factor, and amphetamine + hypothalamic factor simultaneously. Amphetamine at high dosage (20mg/kg) decreased brain norepinephrine (25%), had no effect on dopamine and increased γ-aminobutyric acid levels (78%). Hypothalamic factor (1.0 ml) increased both norepinephrine and dopamine concentrations (51% and 37%, respectively) but had little effect on γ-aminobutyric acid levels. Simultaneous administration of both agents resulted in a decrease in norepinephrine (similar to that seen with amphetamine alone), an increase in dopamine (the same as seen with hypothalamic factor alone), and caused a marked decrease in brain γ-aminobutyric acid levels. The reversal of amphetamine toxicity suggests that the hypothalamic factor may act centrally at the neuronal level. The lethality of amphetamine in the crowded mice situation may be due, in part, to the high level of γ-aminobutyric acid in the brain and which was reversed in the presence of the hypothalamic factor.