Effect
of Fasting and Refeeding on Duodenal Alkaline
Phosphatase Activity in Monosodium Glutamate
Obese Rats
Ľ. RAČEK, Ľ.
LENHARDT 1, Š. MOZEŠ
Institute
of Animal Physiology, Slovak Academy of Sciences,
and 1Department of
Pathology, Veterinary University, Košice, Slovak
Republic
Received
July 4, 2000
Accepted November 16, 2000
Summary
In
the present work the effects of fasting and
refeeding on fat pad weight and alkaline
phosphatase activity in the brush border of
individual duodenal enterocytes have been
evaluated in male Wistar rats with obesity
induced by monosodium glutamate (MSG) treatment
during the early postnatal period. Neonatal rats
were treated subcutaneously with MSG (2 mg/g
b.w.) or saline (controls) for 4 days after
birth. At 4 months of age, two types of
experiments were performed. In the first
experiment rats, were submitted to 3 or 6 days
lasting food deprivation. In the second
experiment the rats were refed for 3 or 6 days ad
libitum or restrictedly (60 % of pre-fasting
intake) after a 6 day-fasting period. Fasting and
refeeding influenced the body fat and function of
the duodenum in MSG-treated rats differently as
compared to the controls. However, alkaline
phosphatase activity and the weight of epididymal
and retroperitoneal fat depots were significantly
increased in MSG obese rats (P<0.001) during
all the periods examined. While 3 days of food
deprivation resulted in both groups in a similar
loss of adipose tissue weight and alkaline
phosphatase activity, the decrements of these
parameters after 6 days of fasting were lower in
obese rats suggesting that their capacity to
spare body fat stores was enhanced. After 3 days
of ad libitum refeeding, a more marked
adaptational increase of food consumption and
also a significantly increased alkaline
phosphatase activity above the pre-fasting level
(P<0.01) was observed in the MSG-treated rats.
Consequently, a more rapid body fat restoration
was demonstrated in these animals. Refeeding of
rats at 60 % of the pre-fasting intake level
resulted in a significant increase of alkaline
phosphatase activity in both the MSG and control
group; moreover, as food restriction continued,
MSG-treated rats tended to further increase the
enzyme activity. Our results revealed that MSG
treatment of neonatal rats may significantly
change the intestinal functions. Permanently
increased alkaline phosphatase activity observed
in MSG obese rats during all investigated periods
suggests that this functional alteration is
probably not a consequence of actual nutritional
variation but could be a component of regulatory
mechanisms maintaining their obesity at critical
values.
Key
words
Fasting/refeeding
· Duodenal alkaline phosphatase · Monosodium
glutamate · Obese rats
Reprint
requests
Dr.
Š. Mozeš, Institute of Animal Physiology,
Slovak Academy of Sciences, Šoltesovej 4., 040
01, Košice, Slovak Republic. E-mail: mozes@saske.sk
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