INVESTIGADORES
SANCHEZ POZZI Enrique Juan
artículos
Título:
Analysis of P-Nitrophenol Glucuronidation in Hepatic Microsomes from Lactating Rats
Autor/es:
LUQUITA, MARCELO G; ENRIQUE JUAN SANCHEZ POZZI; CATANIA, VIVIANA A; MOTTINO, ALDO D
Revista:
BIOCHEMICAL PHARMACOLOGY
Editorial:
PERGAMON-ELSEVIER SCIENCE LTD
Referencias:
Año: 1994 vol. 47 p. 1179 - 1185
ISSN:
0006-2952
Resumen:
In the present study, hepatic p-nitrophenol glucuronidation was analyzed
comparatively in virgin female, lactating mother and nonlactating
mother rats (the last two groups 19-21 days post-partum). Enzyme assays
were performed in native and activated microsomal suspensions.
Activation was achieved either by including UDP-N-acetylglucosamine in
the incubation mixtures or by preincubating native microsomes with
optimal concentrations of Triton X-100 or
palmitoyl-lysophosphatidylcholine. When UDP-N-acetylglucosamine was used
as activator, enzyme activity increased in both lactating (about 80%
increment) and nonlactating mothers (about 30% increment) as compared
with virgin females. From an analysis of the degree of activation by
Triton X-100 and palmitoyl-lysophosphatidylcholine, it can be inferred
that the pregnancy-delivery event decreased the latency of
UDP-glucuronosyltransferase activity that was detectable even 3 weeks
post-partum, irrespective of whether suckling newborns were or were not
kept with their mothers (lactating and nonlactating mothers,
respectively). The estimation of apparent Vmax toward UDP-glucuronic
acid in palmitoyl-lysophosphatidylcholine-activated microsomes, which
allows an estimation of the amount of the enzyme, showed that lactation
increased the number of catalytic units (about 40%). Hepatic
UDP-glucuronic acid content was 70% higher in lactating rats than in
other groups. The lipid composition and membrane fluidity (using
1,6-diphenyl-1,3,5-hexatriene as probe) were also analyzed in microsomes
from all groups. A significant decrease in the unsaturation index that
correlated with the rigidization of microsomal membranes was consistent
with the changes in the degree of enzyme latency observed in lactating
and nonlactating mothers. In conclusion, lactating rats exhibited
enhanced p-nitrophenol UDP-glucuronosyltransferase activity as well as
an increase in the hepatic content of UDP-glucuronic acid. These
findings and the fact that lactation increased the liver to body weight
ratio emphasize the role of the liver in the metabolism of planar
phenolic derivatives in these circumstances.