Drugs online research references
J Cardiovasc Pharmacol. 1989;13 Suppl 2:S38-44; discussion S44.
Regulation of triglyceride mobilization in isolated hepatocytes by dibutyryl cyclic AMP and epinephrine.
Woodside WF, Ontko JA.
Department of Pharmacology, University of New Mexico School of Medicine, Albuquerque 87131.
Regulation of the mobilization of endogenous fatty acids from lipid droplet triglyceride was investigated in isolated hepatocytes from normal-fed rats. Mobilized fatty acid was entirely accounted for in oxidation products (CO2 plus acid-soluble products). Dibutyryl cyclic AMP (DBcAMP) stimulated the mobilization of endogenous fatty acids by over 50% although no change in free fatty acid (FFA) levels was observed. In the presence of tetradecyglycidic acid (TDGA), a specific inhibitor of mitochondrial fatty acid oxidation, DBcAMP was unable to promote endogenous fatty acid oxidation; instead, the nucleotide increased the FFA level. This effect was blocked by the lysosomal inhibitor, chloroquine, supporting the concept that a lysosomal lipase is involved in the degradation of endogenous triglyceride. These findings suggest that cyclic AMP stimulates lysosomal lipolysis by a mechanism that is independent of changes in fatty acid oxidation. Epinephrine alone slightly suppressed triglyceride mobilization. Epinephrine plus doxazosin slightly increased lipid mobilization. Epinephrine plus propranolol suppressed endogenous fatty acid oxidation to a level significantly below that induced by epinephrine plus doxazosin. These results suggest that alpha 1-adrenoceptor activation suppresses hepatic triglyceride mobilization. The weak stimulatory effects of beta-adrenoceptor activation on hepatocyte triglyceride mobilization compared with the potent stimulation by DBcAMP is probably attributable to the relatively low level of beta-adrenoceptors in hepatocytes from the mature male rats used in these studies. Further characterization of a possible mutually antagonistic interaction between alpha 1- and beta 2-adrenoceptors in the regulation of hepatic triglyceride mobilization might be better accomplished in a species with hepatocytes that have a higher proportion of beta-adrenoceptors, e.g., guinea pig, rabbit, and dog.
online pharmacy ref source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=2471014&dopt=Abstract
J Cardiovasc Pharmacol. 1989;13 Suppl 2:S45-9; discussion S49.
Effect of doxazosin on plasma lipids and atherogenesis: a preliminary report.
Kowala MC, Nicolosi RJ.
Department of Clinical Sciences, University of Lowell, Massachusetts 01854.
Chronic treatment with selective alpha 1-inhibitors has a beneficial impact on plasma lipids and arterial pressure. To study the effect of selective alpha 1-inhibition on atherogenesis, gerbils and hamsters were fed rodent chow containing 0.2% cholesterol and 10% coconut oil (by weight). One group of each species received the selective alpha 1-inhibitor doxazosin (gerbil, 17 mg/kg/day; hamster, 11 mg/kg/day) in the diet. In gerbils treated for 6 weeks with doxazosin, plasma total cholesterol fell by 39% and very-low-density lipoprotein (VLDL) plus low-density lipoprotein (LDL) cholesterol by 52% compared with control levels. Plasma triglyceride and high-density lipoprotein (HDL) cholesterol were unaffected. In hamsters treated with doxazosin for 6 weeks, plasma total cholesterol, VLDL plus LDL cholesterols, and triglyceride were reduced by approximately 40% compared with hyperlipidemic controls. HDL cholesterol, mean arterial pressure, and heart rate were not significantly altered. Using en face preparations of the hamster aortic arch, intimal macrophage-derived foam cells were quantitated. Compared with controls, doxazosin reduced the number of intimal foam cells/mm2 by 71%. We suggest that selective alpha 1-inhibition reduces foam cell accumulation by lowering plasma lipids and/or by a direct effect on the arterial wall.
online pharmacy ref source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=2471015&dopt=Abstract
J Cardiovasc Pharmacol. 1989;13 Suppl 2:S5-9; discussion S9-10.
Effects of doxazosin on lipids, lipoprotein lipases, and cholesterol synthesis in the golden hamster.
Jansen H, Lammers R, Baggen MG, Birkenhager JC.
Department of Internal Medicine III, Erasmus University Rotterdam, The Netherlands.
The effects of treatment with adrenoceptor blockers on sites regulating lipid metabolism were studied in golden hamsters. In hamsters fed a standard chow, doxazosin, propranolol, and atenolol did not affect plasma cholesterol or triglycerides. After hypercholesterolemia was induced by feeding a cholesterol-enriched diet, doxazosin lowered plasma cholesterol by 12%. Lipoprotein lipase activity in adipose tissue and in the heart was not changed by any of the treatments. Hepatic lipase activity in the liver and blood was lowered by 31% in the doxazosin-treated animals. Hepatic cholesterol synthesis, measured as acetate incorporation into cholesterol and hydroxymethylglutaryl coenzyme A (HMG-CoA) reductase activity, was also lowered in the doxazosin-treated hamsters. After norepinephrine administration to cholesterol-fed hamsters, atenolol increased (+8%) and doxazosin decreased (-35%) plasma triglycerides. Plasma cholesterol levels and hepatic cholesterol synthesis were no longer significantly affected by doxazosin. In norepinephrine-treated animals, adipose tissue lipoprotein lipase activity was enhanced (+30%) by doxazosin. Hepatic lipase activity in plasma and liver, which was lowered by norepinephrine, was increased by doxazosin. In hamsters not treated with norepinephrine, adrenoceptor blockers had no effect on plasma insulin or thyroid hormone, but with norepinephrine, levels of both insulin and thyroid hormone were increased by doxazosin. These data indicate that selective alpha 1-inhibition with doxazosin may interfere with lipid metabolism at several regulatory sites. The effects depend to a large extent on nutritional and hormonal status. Doxazosin might exert these effects partly via influences on other hormones.
online pharmacy ref source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=2471016&dopt=Abstract
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