The maturation of oxidative phosphorylation in human mitochondria and its relation to increased adenine nucleotide concentration

Abstract

Transition from a uterine environment to an independent existence requires the maturation of energy production. Foetalrat liver mitochondria show a rapid increase in respiratory activity aRer birth, dependent on a net uptake of adenine nucleotides (Sutton & Pollak, 1980). The present work examines the relationship between oxygen consumption in the presence of three substrates by human placental and uterine mitochondria and their adenine nucleotide contents. Placentae were obtained from uncomplicated deliveries (gestations 36-41 weeks) and non-pathological uterine tissue from hysterectomies. Mitochondria were prepared and assayed by the methods of Olivera & Meigs (1975), with the exception of the preparation and assay media. Isolation buffer contained 0.22 M - mannitol, [4 - (2 hydroxyethy1)- 1 -piperazine-ethanesulphonic acid1 and 1 mMEDTA, pH7.4, with the addition of 2mg of bovine serum albumin/ml. Assay buffer was similar but also contained lOmM-KH,PO,, 5 mM-MgCl, and fatty acid-free bovine serum albumin. Adenine nucleotides were extracted from both uterine and placental mitochondria and assayed by high-pressure liquid chromatography (Simmonds et al., 1982).