ABSTRACT
The IGF system is one of the most important endocrine and paracrine growth factor systems that regulate fetal and placental growth. We hypothesized that intrauterine growth restriction (IUGR) in guinea pigs is mediated by the altered expression of IGFs and/or IGF binding protein (BP) mRNAs in tissues and is related to growth of specific tissues. IUGR was induced by unilateral uterine artery ligation on day 30 of gestation, and fetal plasma, amniotic fluid and tissue samples were collected at 55-57 days (term about 68 days) from paired IUGR and control fetuses (n=6). Western ligand blotting and immunoblotting were used to compare IGFBP levels in plasma and amniotic fluid. Total RNA was extracted from placenta and fetal tissues, and the relative abundance of IGF-II and IGFBP-1-6 mRNA was determined by Northern blotting, using species-specific probes where available. IUGR fetuses had decreased (P<0.01, by Student's t-test) placental weight and body weight with an increase in the brain:liver weight ratio. The principal IGFBPs in fetal plasma migrated at 40-35, 30 and 25 kDa and were identified as IGFBP-3, -2 and -4 respectively. IUGR was associated with elevated plasma IGFBP-2 and IGFBP-4 and reduced IGFBP-3 levels. IGFBPs were detected at low levels in amniotic fluid of control fetuses but at higher levels in IUGR fetuses. In IUGR placentae, there was a small increase in IGFBP-4 mRNA (P<0.05). IGFBP-2 mRNA increased (P<0.001) in liver of IUGR fetuses. IGF-II and IGFBP mRNA expression did not change in fetal muscle. The results are consistent with reduced IGF action, directly or through inhibition by IGFBPs, particularly by circulating and tissue IGFBP-2, as a potential causal factor in decreased growth of the placenta and certain fetal tissues.
Subject(s)
Fetal Growth Retardation/metabolism , Insulin-Like Growth Factor Binding Proteins/metabolism , Insulin-Like Growth Factor II/metabolism , Amnion/chemistry , Animals , Blotting, Northern/methods , Blotting, Western/methods , Female , Fetal Blood/chemistry , Gestational Age , Guinea Pigs , Insulin-Like Growth Factor Binding Protein 2/blood , Insulin-Like Growth Factor Binding Protein 2/metabolism , Insulin-Like Growth Factor Binding Protein 3/blood , Insulin-Like Growth Factor Binding Protein 3/metabolism , Insulin-Like Growth Factor Binding Protein 4/blood , Insulin-Like Growth Factor Binding Protein 4/metabolism , Insulin-Like Growth Factor Binding Proteins/analysis , Insulin-Like Growth Factor Binding Proteins/blood , Insulin-Like Growth Factor II/genetics , Liver/chemistry , Models, Animal , Placenta/chemistry , Pregnancy , RNA, Messenger/analysis , Reverse Transcriptase Polymerase Chain ReactionABSTRACT
A shuttle-borne radiometer containing ten channels in the reflective infrared has demonstrated that direct identification of carbonates and hydroxyl-bearing minerals is possible by remote measurement from Earth orbit.
Subject(s)
Lipase/blood , Lipoprotein Lipase/blood , Triglycerides , Adipose Tissue/enzymology , Animals , Chylomicrons/blood , Humans , Hyperlipoproteinemia Type I/blood , Hyperlipoproteinemia Type V/blood , Kinetics , Lipoproteins, HDL/blood , Lipoproteins, LDL/blood , Liver/enzymology , Rats , Substrate Specificity , Tangier Disease/bloodABSTRACT
Apolipoprotein C-II (apoC-II) is a small protein found associated with the plasma lipoproteins. It serves a unique function in the activation of the enzyme lipoprotein lipase (triacylglycerol acyl-hydrolase, EC 3.1.1.3). ApoC-II contains a single arginine residue, permitting tryptic cleavage into two peptides after succinylation of the native protein. The succinylated amino-terminal peptide, approximately 50 residues, did not activate lipoprotein lipase. The succinylated carboxyl-terminal peptide, about 29 residues, had significant cofactor activity. Relative to native apoC-II, the maximal activation observed with the succinylated carboxyl-terminal peptide was 50% lower and the concentration required for half-maximal activity was approximately 10 times higher. Mixtures of the carboxyl- and amino-terminal peptides had no more activity than the carboxyl-terminal peptide alone. Localization of functional properties to the carboxyl region is a feature also common to apolipoproteins C-III, A-II, and A-I.
