Purine Metabolism in High- and Low-Uric Acid Lines of Chickens: Hypoxanthine/Guanine Phosphoribosyltransferase Activities

Abstract

The activity of hypoxanthine/guanine phosphoribosyltransferase (HGPRT) was examined in the livers and kidneys of two genetic lines of chickens selected for different plasma uric acid levels. Previous work demonstrated that the high-uric acid line (HUA) had significantly greater de novo uric acid synthesis rates in kidney tissue compared to the low-uric acid line (LUA). In addition, phosphoribosylpyrophosphate (PRPP) synthetase and xanthine dehydrogenase activities in livers and kidneys were significantly higher in the HUA compared to the LUA line. PRPP pool sizes were also significantly higher in both livers and kidneys of HUA birds. HGPRT activities in livers of HUA birds were significantly (P -c 0.05) greater than in LUA birds. The mean value of liver HGPRT was 7.36 f 0.25 pmole inosine-5'-monophosphate (IMP) and 6.05 f 0.27 pmole IMP produced/pg protein/hr, respectively, for the HUA and LUA lines. There were no significant differences (P > 0.05) in kidney HGPRT activities between the two groups. The mean value of kidney HGPRT was 52.87 f 1.62 pmole IMP and 50.72 f 1.62 pmole IMP produced/pg protein/hr, respectively, for the HUA and LUA line. Elevated liver HGPRT may serve to enhance the regeneration of PRPP in the HUA liver. Elevated liver PRPP synthetase and PRPP pool size suggest an increased flux through the de novo purine biosynthetic pathway in HUA birds. The resulting additional pyrophosphate from the glutamine PRPP amidotransferase reaction would stimulate recovery of PRPP and spare the system from a substantial loss of energy.

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“…Both enzymes can be inhibited by the synthetic products IMP, AMP, and GMP [ 102 , 103 ]. The increase of PRP can promote the activity of PRPPAT and accelerate the production of ribose 5-phosphate [ 104 ]. Interestingly, in a preliminary experiment we performed, the mRNA levels of PRPS and PRPPAT in the kidneys of goslings infected with GAstV were significantly upregulated compared with the control group (data not published).…”

“…The enzymes involved in purine nucleotide salvage synthesis are adenine phosphoribosyl transferase (APRT) and hypoxanthine-guanine phosphoribosyl transferase (HGPRT) [ 104 , 110 ]. Human cytomegalovirus infection can significantly increase the mutation frequency of the HGPRT gene.…”

“…In addition, nephropathogenic IBV infection resulted in increases in renal XO gene transcription and serum XO activity, leading to hyperuricemia and reduction of antioxidants in the body [107]. The enzymes involved in purine nucleotide salvage synthesis are adenine phosphoribosyl transferase (APRT) and hypoxanthine-guanine phosphoribosyl transferase (HGPRT) [104,110]. Human cytomegalovirus infection can significantly increase the mutation frequency of the HGPRT gene.…”

Purine Metabolism in High and Low Uric Acid Lines of Chickens: De Novo Uric Acid Synthesis in Isolated Hepatocytes and Phosphoribosylpyrophosphate Amidotransferase Activities

“…PRPP amidotransferase activity was linear with respect to protein concentration and time. Acetone powders of both livers and kidneys were prepared as previously described (14,15). Thirty milligrams of each acetone powder preparation was extracted in 4 ml of 25 mMTris-HCl buffer, pH 7.0, containing 3 mM MgC12 and 1 mM p-mercaptoethanol using a glass-teflon homogenizer (Arthur H. Thomas Co., Philadelphia, Pa.).…”

“…Blood samples were taken via cardiac puncture using heparinized syringes. Plasma uric acid levels (14,15) were determined by a micromethod modification ( 17) of the uricase spectrophotometric procedure of Feichtmeir and Wrenn (18).…”