ABSTRACT
The accumulation of alpha-aminoisobutyric acid by placental slices is increased dramatically upon prior incubation of the slices in amino acid-free, buffered saline. This increase is inhibited by inhibitors of protein synthesis and is accompanied by an increased V for the transport process. While alternative explanations are discussed, these data suggest that the incubation effect may be mediated through an increase in the number of available transport sites which are synthesized during the incubation period. Incubation with an amino acid mixture diminishes the increase as well as general protein synthesis, suggesting that a reduced availability of amino acids may initiate compensatory changes in the synthesis of cellular transport proteins.
Subject(s)
Aminoisobutyric Acids/metabolism , Placenta/metabolism , Amino Acids/pharmacology , Biological Transport , Cycloheximide/pharmacology , Female , Humans , In Vitro Techniques , Kinetics , Placenta/drug effects , Pregnancy , Puromycin/pharmacologyABSTRACT
We describe a rapid radioimmunoassay for human placental lactogen in biological fluids, with use of polyethylene glycol to separate free from antibody-bound placental lactogen. The standard curve obtained, easily fitted to a logit-log transformation, is useful over a concentration range of 6 to 400 ug/liter. Within-assay variability is 1.97%, between-assay variability 2.20%. The relation is linear when lactogen added is plotted against that accounted for analytically, the actual recovery being 100.26%.
Subject(s)
Placental Lactogen/analysis , Polyethylene Glycols , Antibody Specificity , Humans , Placental Lactogen/blood , Radioimmunoassay/methodsABSTRACT
Tyrosine aminotransferase is present at low activity in the rabbit placenta. The activity can be enhanced by injecting the pregnant mother with insulin or cortisol. This response decreases over the last half of gestation (14-28 days gestational age).