Sm. Khoja et al., EFFECT OF VANADATE ON THE ACTIVITY OF RAT JEJUNAL 6-PHOSPHOFRUCTO-1-KINASE, Comparative biochemistry and physiology. Part C, Pharmacology toxicology & endocrinology, 115(3), 1996, pp. 217-221
The effect of sodium orthovanadate on the activity of 6 phosphofructo-
1-kinase (PFK) in the epithelial cells of rat: small intestine was inv
estigated. Injection of vanadate (2.5 mg/rat) into rats at 2-day inter
vals per week for two consecutive weeks resulted in a significant decr
ease in the maximal activities and activity ratios (activity at 0.5 mM
fructose-6-phosphate at pH 7.0/activity at pH 8.0 [v(0.5)/V]) of the
partially purified PFK in rat jejunum. Also, the sensitivity of jejuna
l PFK to inhibition by ATP increased in rats treated with vanadate. Th
e addition of 1 mu M fructose-2,6-biphosphate and 50 mu M AMP in the a
ssays released the enzyme inhibition by ATP, and no significant differ
ence was seen between vanadate-injected and control rats. Moreover, th
e extent of activation with 1 mu M fructose-2,6-bisphosphate was signi
ficantly higher (79%) in vanadate-injected rats than in control rats (
26%). The present results indicate that rat jejunal PFK is highly inhi
bited with vanadate in vivo. Therefore, although vanadate has been con
sidered to be an insulin-like agent, because of its insulin like effec
ts on adipocytes and skeletal muscle, the present results may indicate
that this behavior could not be applicable to normal rat tissues, bec
ause the effect of vanadate on jejunal PFK is clearly opposite that of
insulin. Copyright (C) 1996 Elsevier Science Inc.