Factors affecting ascorbic acid biosynthesis in chickens. I. Adaptation of an assay and the effect of age, sex and food deprivation

Abstract

Summary The objective of this study was to adapt an assay to measure L‐gulonolactone oxidase (GLO) activity, the final step in ascorbate synthesis, in chickens and use the procedure to study the effect of gender, age, and food deprivation. To adapt a procedure used for mammalian tissues the kinetic constants were estimated using chicken kidney and assay conditions optimized in terms of storage of tissue and homogeneity of distribution. A series of experiments were conducted using the standardized assay with individual animals as the experimental unit. Gender differences were detected only in mature birds with male chickens having lower GLO activity than females. Time‐course changes in GLO activity in immature chicks were best characterized by a segmented response function consisting of a parabola joined to a straight line. The maximum value was estimated to occur at 13 days and from day 16 declined linearly. The functional relationship did not provide evidence of an early lag period or a peak at 4 weeks in immature chickens. Food deprivation in matched groups of birds demonstrated the effect of food on GLO activity in chickens. Food and water deprivation for 12 h and food deprivation for 24 h had no significant effect on GLO activity. Food deprivation for 48 h caused a significant decrease in GLO activity and it was not further depressed by deprivation for 72 h. Initial GLO activity was restored within 24 h of repletion. The results clearly demonstrated that gender, age, and starvation are determinants of ascorbate synthesis in chickens.

Factors affecting ascorbic acid biosynthesis in chickens: III. Effect of dietary fluoride on l‐gulonolactone oxidase activity and tissue ascorbic acid (AsA) concentration

“…Poultry are renal synthesizers of ascorbic acid (AsA) (Grollman and Lehninger, 1957) and diets are not normally fortified. The kinetic constants of chicken l-gulonolactone oxidase (GLO) and time course changes in activity (Hooper et al, 2000) are similar to results reported for rats (Chatterjee and McKee, 1965) and gender differences were similar to those reported for dogs and rabbits with activity lower in males. A common assumption is that biosynthesis may be inhibited or turnover increased in the presence of stressors and supplementation may be beneficial (Coates, 1984;Hornig et al, 1984;Peebles and Brake, 1985;Gross, 1988;Kutlu and Forbes, 1993;McKee and Harrison, 1995;Amakye-Anim et al, 2000).…”

“…Tissue samples were processed and assayed within 3 weeks storage at −20 °C. Renal GLO (EC 1.1.3.8) activity was assayed within 2 weeks of tissue collection ( Hooper et al, 2000). A blank was run with each sample to correct for endogenous AsA in the renal homogenate.…”

“…A common assumption is that biosynthesis may be inhibited or turnover increased in the presence of stressors and supplementation may be beneficial ( Coates , 1984; Hornig et al, 1984; Peebles and Brake , 1985; Gross , 1988; Kutlu and Forbes , 1993; M c K ee and Harrison , 1995; Amakye‐Anim et al, 2000). Food deprivation (12–48 h) as a stressor did not alter GLO activity but enzyme activity decreased after 72 h and was restored within 24 h of repletion ( Hooper et al, 2000).…”

Ascorbic acid biosynthesis in hens producing strong and weak eggshells

“…The samples were maintained in ice, plasma separated by centrifugation and ascorbic acid determined within 4 h of collection (Hooper et al, 2000). The birds were killed by exposure to carbon dioxide and the distal portion of the left kidney, the adrenal glands and liver were sampled, wrapped in aluminium foil, kept in a plastic bag immersed in slush ice and later stored at À20 C. Liver samples and adrenal glands were homogenised in 10 volumes of 5% cold trichloroacetic acid for 10 s using a Polytron homogeniser.…”

“…The homogenate was centrifuged at 12 000 g and 4 C for 2 min and the supernatant used to measure ascorbic acid (Creel et al, 2001). The liver and adrenal gland samples were processed within 4 weeks of storage at À20 C. Renal L-gulonolactone oxidase [EC 1.1.3.8] activity was assayed within 2 weeks of tissue collection (Hooper et al, 2000). A blank was performed with each sample to correct for endogenous ascorbic acid.…”