TY - JOUR T1 - Metabolic clearance rate of dopamine beta-hydroxylase in the rat. JF - Molecular Pharmacology JO - Mol Pharmacol SP - 112 LP - 120 VL - 23 IS - 1 AU - J M Stolk AU - J H Hurst AU - R B Guchhait AU - G Vantini AU - G P Lefort AU - B C Nisula Y1 - 1983/01/01 UR - http://molpharm.aspetjournals.org/content/23/1/112.abstract N2 - The metabolic clearance rate (MCR) of both bovine and rat dopamine beta-hydroxylase (DBH) preparations was measured using two complementary procedures, pulse-dose injection and constant infusion of enzyme into the rat circulation. Rats that received injections of DBH activity had plasma DBH activity levels similar to those of controls by 24 hr after a pulse dose of rat DBH. The DBH MCR computed by stochastic analysis of the disappearance curve of injected DBH activity was about 1.0 ml/hr/100 g body weight; the mean transit time of DBH was about 8 hr. The disappearance curve of heterologous enzyme (bovine DBH) was more rapid than that of the rat, yielding an MCR of about 8 ml/hr/100 g body weight. MCR values obtained with the constant-infusion technique were similar to those obtained with the pulse-dose technique. These kinetic parameters are consistent with the time frame for altered plasma DBH activity observed with pharmacological and endocrinological factors. These data support the conclusion that plasma DBH turnover time is measured in hours, not days. ER -