ABSTRACT
Significant differences were found in the rates of lipogenesis, glucose oxidation and lipolysis in porcine adipose tissue from four depots; outer subcutaneous (OSC), middle subcutaneous (MSC), perirenal (PR) and omental (OM). Lipogenesis was stimulated by insulin in all depots in the order PR > OM > MSC > OSC. Lipolysis was stimulated by isoproterenol in all depots in the order PR > OM > MSC > OSC. Differences in lipid metabolism by the different depots may have an important impact on lipid accretion in vivo.
Subject(s)
Adipose Tissue/drug effects , Insulin/pharmacology , Isoproterenol/pharmacology , Lipid Metabolism , Adipocytes/cytology , Adipocytes/drug effects , Adipocytes/metabolism , Adipose Tissue/metabolism , Animals , Cell Size , Dose-Response Relationship, Drug , Glucose/metabolism , Kidney , Lipolysis/drug effects , Male , Omentum , Oxidation-Reduction , Skin , Swine , Tissue DistributionABSTRACT
N-Acetylneuraminic acid (Neu5Ac) and N-glycoloylneuraminic acid (Neu5Gc) are distributed widely in nature. Using a Carbopac PA-1 anion exchange column, we have determined the ratios of Neu5Ac and Neu5Gc in hydrolysates of platelets and their precursors: a rat promegakaryoblastic (RPM) cell line and a human megakaryoblastic leukemia cell line (MEG-01). The ratio of Neu5Gc:Neu5Ac in cultured RPM cells is 16:1, whereas in platelet rich plasma and cultured MEG-01 cells it is 1:38 and 1:28, respectively. The nature of these sialic acids from RPM cells was verified using thin layer chromatography and liquid secondary ion mass spectrometry. The relevance of increased Neu5Gc levels in early stages of development is discussed.
Subject(s)
Blood Platelets/metabolism , Neuraminic Acids/blood , Sialic Acids/blood , Animals , Chromatography, Ion Exchange , N-Acetylneuraminic Acid , RatsABSTRACT
Rat promegakaryoblasts (RPM, a precursor platelet cell line) in culture exhibited a capacity to bind, take up and degrade 125I-LDL. The low density lipoprotein (LDL) binding showed the following characteristics: (a) high affinity, (b) saturability, (c) specificity, (d) down-regulation, after exposure to 25 hydroxycholesterol. Furthermore the proteolytic degradation of 125I-LDL by RPMs was inhibited by chloroquine which interferes with the lysosomal degradation processes. These findings show LDL receptor cell biology of RPM to be of the classical type and to differ from that of platelets.
