title: The bioavailability and disposition kinetics of genistein in cats.
abstract: The absorption and disposition kinetics of the soy isoflavone genistein were determined in cats (n = 6). An oral dose of 100 mg/kg was administered, which has previously been demonstrated to be the minimum oral estrogenic dose, and was administered intravenously at a dose of 20 mg/kg, being the largest practical dose that could be safely administered. Plasma free, and total (conjugated + free) genistein concentrations were determined by HPLC following organic extraction. Noncompartmental analysis revealed a half-life of 21.67 +/- 7.9 h (free) and 9.95 +/- 2.7 h (conjugated), volume of distribution 31.94 +/- 10.38 L/kg (free) and 11.82 +/- 3.96 L/kg (conjugated) following intravenous administration. Following oral administration the half-lives were determined to be 17 +/- 4.8 h (free) and 8.56 +/- 4.65 h (conjugated), with tmax = 4.4 +/- 0.6 h (free) and 4.42 +/- 0.99 h (conjugated), and Cmax = 0.276 +/- 0.1 microg/mL (free) and 6.24 +/- 6.58 microg/mL (conjugated). Oral bioavailabilities were 1.379 +/- 0.9% (free) and 29.85 +/- 22.61% (conjugated). The ratio of total:free genistein ranged from 25.9 to 5.5. Poor oral absorption and efficient conjugation explain the low bioavailability of free genistein. Accumulation of genistein in peripheral lipophilic compartments may occur.
authors.affiliation: Institute of Veterinary, Animal and Biomedical Sciences, Massey University, Palmerston North, New Zealand. n.j.cave@massey.ac.nz
authors.forename: N J
authors.initials: NJ
authors.lastname: Cave
authors.forename: R C
authors.initials: RC
authors.lastname: Backus
authors.forename: S L
authors.initials: SL
authors.lastname: Marks
authors.forename: K C
authors.initials: KC
authors.lastname: Klasing
mesh_terms: D000284:Administration, Oral; D000818:Animals; D019540:Area Under Curve; D001682:Biological Availability; D002415:Cats / Q000378:metabolism*; D002851:Chromatography, High Pressure Liquid; D005260:Female; D019833:Genistein / Q000008:administration & dosage / Q000097:blood / Q000493:pharmacokinetics*; D007275:Injections, Intravenous / Q000662:veterinary; D008297:Male; D048789:Phytoestrogens / Q000008:administration & dosage / Q000097:blood / Q000493:pharmacokinetics*
chemical_list: D048789:Phytoestrogens; D019833:Genistein