title: Sex differences in the enzymatic hydrolysis of acetylsalicylic acid by microsomes from various rat tissues.
abstract: We studied the in vitro hydrolysis of acetylsalicylic acid (ASA) to salicylic acid (SA) catalysed by microsomal preparations from liver, kidney, small intestine and stomach mucosas and blood serum of adult female and male rats. Hepatic microsomes from male rats had the highest specific activity: 42.3 +/- 6.0 nmol SA mg(-1) min(-1) (mean +/- SEM). Kidney, intestine, stomach and serum activities were 60, 30, 14 and 0.7% with regard to the liver. In contrast, gastric microsomes from female rats showed the highest specific activity: 53 +/- 22.1 nmol SA mg(-1) min(-1) (mean +/- SEM) whereas intestine, liver, kidney and serum activities were 60, 43, 40 and 1.7% with regard to the stomach mucosa. Hepatic, renal and intestinal microsomes had a pH optimum of 5-6. Male rats had Vmax and Km values of 95.5, 83.4 and 29.4 nmol SA mg(-1) min(-1) and 2.9, 1.27 and 6.4 mM, while for female rats they were 54.8, 75.8 and 59.4 nmol SA mg(-1) min(-1) and 2.6, 1.35 and 3.4 mM for hepatic, renal and intestinal microsomes, respectively. Parathion inhibited the hydrolysis of ASA with an IC50 of 1.2 x 10(-5) M for liver and kidney and 5 x 10(6) M for intestine from male rats.
authors.affiliation: Departamento de Farmacología y Toxicología, Centro de Investigación y de Estudios Avanzados del I.P.N., México, D.F., Mexico.
authors.forename: A M
authors.initials: AM
authors.lastname: Vargas Loza
authors.forename: E I
authors.initials: EI
authors.lastname: Montes de Oca
authors.forename: F A
authors.initials: FA
authors.lastname: Posadas del Rio
mesh_terms: D000818:Animals; D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000378:metabolism*; D001241:Aspirin / Q000378:metabolism*; D001711:Biotransformation; D002265:Carboxylic Ester Hydrolases / Q000378:metabolism*; D002800:Cholinesterase Inhibitors / Q000494:pharmacology; D005260:Female; D005753:Gastric Mucosa / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D007413:Intestinal Mucosa / Q000378:metabolism; D007668:Kidney / Q000378:metabolism; D008099:Liver / Q000378:metabolism; D008297:Male; D008861:Microsomes / Q000187:drug effects / Q000201:enzymology*; D010278:Parathion / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D012459:Salicylates / Q000378:metabolism; D020156:Salicylic Acid; D012727:Sex Characteristics
chemical_list: D000894:Anti-Inflammatory Agents, Non-Steroidal; D002800:Cholinesterase Inhibitors; D012459:Salicylates; D010278:Parathion; D002265:Carboxylic Ester Hydrolases; D020156:Salicylic Acid; D001241:Aspirin