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The pentose phosphate pathway or the hexose monophosphate shunt is involved in
generation of reducing equivalents NADPH required for reductive biosyntheses and for
maintaining cellular integrity. This pathway is also responsible for the production of
ribose-5-phosphate necessary for nucleotide synthesis. This pathway contains two enzymes:
glucose-6-phosphate dehydrogenase (G6PD) and 6-phosphogluconate dehydrogenase (6PGD) which
generates NADPH from Nicotinamide Adenine Dinucleotide
Phosphate (NADP+). The activity of the former enzyme is rate limiting for the pathway (Levy, 1979). The activity of G6PD is
regulated under different metabolic (Nagayama et al., 1972; Kahn et al., 1977; Mamaev et al., 1977; Marc and Portet, 1981; Mayes, 1988; and Szepesi and Kamara, 1986) and
hormonal conditions (Garcia and Holten, 1974; Aruldhas et al., 1982; Martins et al., 1985; Niortet al., 1985; Fritz and Kletzien, 1987; Peragon et al., 1989; Sabrasua et al., 1989;
Haghighi et al., 1989; 1994; and 2005; Haghighi and Ghanbari, 1991; and Fernando et al., 1992).
It appears that works pertaining to hormonal regulation in G6PDH activity in tissues
of poikilothermic animals are rather meager. Particularly, such studies are completely lacking
in amphibian species. Considering the fact that the enzyme has significant adaptive values
as an alternate bypass mechanism in carbohydrate metabolism and the fact that this route
is involved in the production of NADPH required for reductive biosyntheses and
indirectly involved in constant supply of pentose-phosphates necessary for nucleotide synthesis,
the present work is aimed at studying the effect of the hormone adrenaline on the activity
of the above enzyme in the liver of common Indian toad, Bufo melanostictus. |
