Phosphatase activities in rat liver before and after birth.

Abstract

Several phosphatase enzymes have been studied biochemically and cytochemically to ascertain whether there are ontogenic changes in level or location. Nucleoside monophosphatase (5′-nucleotidase) and lysosomal acid phosphatase are low in foetal liver and, unlike glucose-6-phosphatase, are still quite low in neonatal liver. Bile canaliculi show strong staining for 5′-nucleotidase in adult liver but not in foetal or neonatal liver. Nucleoside diand triphosphatase activities in foetal liver are already near half the adult level. The diphosphatase that is active towards UDP shows the same cytochemical locations in neonatal liver as in adult liver. Triphosphatase activity in foetal and neonatal liver is located largely in ‘star-like’ cells, rather than in the bile canaliculi of parenchymal cells. Biochemical comparison of foetal, neonatal and adult liver has shown that inorganic pyrophosphatase (assayed without Mg2+) parallels glucose-6-phosphatase, but acid ribonuclease does not parallel acid phosphatase. In albino rats injected with thyroxine, glucose-6-phosphatase has shown a more marked increase in foetal liver than in adult liver, although the uptake of thyroxine seemed to be less. In hooded rats, foetal liver showed a negligible uptake of thyroxine and no rise in glucose-6-phosphatase.