Oxidative stress in the pancreas of experimentally induced diabetic rats

✍ Scribed by J. Kalra; R. Kakkar; K. Prasad

• Publisher: Elsevier Science
• Year: 1995
• Tongue: English
• Weight: 121 KB
• Volume: 28
• Category: Article
• ISSN: 0009-9120
• DOI: 10.1016/0009-9120(95)91403-p

✦ Synopsis

There is considerable evidence that phosphatidate (PA) and Iysophosphatidate (LPA) are important second messengers in sisnal transduotion processes in a variety of nell types. Objecti~s It. To determine the ability of PA and LPA to serve as substrates for the placental, intestinal and tissue nonspeeifio isoenzymes of alkaline phosphatase (ALP). b. To assess the importance of ALP in the catabolism of PA and LPA. Methods PA hydrolysis was measured by the conversion of [sH]PA to [SH]diacylglynerul and by the ability of PA to serve as a competitive inhibitor of the hydrolysis of p-nitrophenyl-phosphate (p-NPP). LPA hydrolysis was measured by the ability of LPA to serve as a competitive inhibitor of the hydrolysis of p-NPP. Results The placental imenzyme hydrolyzed PA at the rate of 7 nmol/ rain/unit Of ALP activity, and the tissue nonspeeifio isnenzyme at 10',6 of this. p-NPP was a competitive inhibitor of the PA phospho-hydrolase activity of placental ALP (K, -0.13 raM), and PA was a competitive inhibitor of its p-NPPase activity (I~ = 0.85 mM). LPA was also a compatitive inhibitor of the p-HPPase activity (K~ -0.15 rental/L). Both Ca ~ and Mg ~ inhibited the PA phosphohydmlase activity of placental ALP. Conclusions e. Human AI.Ps will hydrolyze PA and LPA. b. The monovalent salt form of PA is the substrate, e. PA is an unlikely physiological substrate for ALP, but LPA is a better candidate.