IN-VIVO FORMATION OF A SCHIFF-BASE OF AMINOGUANIDINE WITH PYRIDOXAL-PHOSPHATE

Aminoguanidine (AG) is considered to be a promising compound for the t reatment of diabetic complications. We examined the in vitro and in vi vo formation of Schiff bases of AG with pyridoxal 5'-phosphate (PLP) a nd pyridoxal (PL). AG reacted in vitro far more rapidly with PLP to fo rm a Schiff base (PLP-AG) than with PL to form another Schiff base (PL -AG). Administration of AG at 7 mM in drinking water for 18 weeks caus ed the formation of PLP-AG in the liver and kidney of mice (12.1 +/- 1 .6 and 3.8 +/- 0.64 nmol/g of tissue, respectively, mean +/- SD, N = 6 ). The amount of PLP in the liver of mice AG administered was signific antly lower than that of control mice (4.0 +/- 1.4 vs 17.4 +/- 1.3 nmo l/g of wet tissue, mean +/- SD, N = 6). Simultaneous administration of pyridoxine (1 mM in drinking water) with AG (7 mM in drinking water) did not ameliorate the decrease in tissue PLP and caused the excess fo rmation of PLP-AG. The results suggest that attention should he paid t o the deficiency of tissue PLP in the clinical use of AG. (C) 1998 Els evier Science Inc.