Effects of the oestrous cycle and exogenous ovarian steroids on metabolism of beta-phenylethylamine in rat lung.
1 Metabolism of [14C]-beta-phenylethylamine (PEN), a substrate for monoamine oxidase-B (MAO-B), was measured in lung homogenates and in perfused lungs during the 4 day oestrous cycle of the rat. 2 Metabolism in vitro was high during met-oestrus and di-oestrus and low during pro-oestrus and oestrus; this variation in activity correlated with changes in Vmax of the enzyme without changes in Km. 3 PEN metabolism in lung homogenates was also altered by treatment of rats with 17 beta-oestradiol but not by progesterone treatment. 4 Metabolism of [14C]-PEN in perfused lungs was the same during either pro-oestrus or met-oestrus. Uptake of [14C]-PEN in perfused lung measured directly was also the same at these two stages. 5 These results demonstrate that in lungs MAO-B activity was affected by endogenous changes in steroid level but that such changes in enzymic activity were not reflected in the metabolic properties of whole lung.
D000818:Animals; D004958:Estradiol / Q000494:pharmacology*; D004971:Estrus; D005260:Female; D066298:In Vitro Techniques; D007700:Kinetics; D008168:Lung / Q000187:drug effects / Q000378:metabolism*; D010627:Phenethylamines / Q000378:metabolism*; D011247:Pregnancy; D011374:Progesterone / Q000494:pharmacology*; D051381:Rats
D010627:Phenethylamines; D011374:Progesterone; D004958:Estradiol