THE EFFECTS OF A SELECTIVE ALPHA-1-ADRENERGIC BLOCKADE ON THE ACTIVITY OF ADIPOSE-TISSUE LIPOPROTEIN-LIPASE IN FEMALE HAMSTERS

Lipoprotein Lipase, is an enzyme responsible for the hydrolysis of tri acylglycerols at the surface of endothelial cells. Its regulation is n ot completely elucidated and seems, among other things, under the infl uence of the sympathetic nervous system. The adrenergic regulation of lipoprotein lipase activity is complex and the alpha(1) adrenergic pat hway appears involved in this regulation. In the present study, adipos e tissues of female hamsters are investigated following a single injec tion of doxazosin and phenylephrine and are compared to controls for t he activity of lipoprotein lipase. After an acute treatment with a sel ective alpha(1) antagonist (doxazosin), lipoprotein lipase activity wa s decreased in the parametrial white adipose tissue and increased in b rown adipose tissue (p less than or equal to 0.05). Moreover, a treatm ent with phenylephrine; an alpha(1) adrenergic agonist, increased the activity of lipoprotein lipase, in the parametrial fat pad only. On th e other hand, the activity of Lipoprotein lipase in heart and in skele tal muscle was not modified by an alpha(1) stimulation or blockade. In this study, calcium and norepinephrine did not appear involved in the regulation of lipoprotein lipase activity. On the contrary, the incre ase of plasma glycerol after an acute treatment with doxazosin suggest s that the lipolytic activity of white adipose tissue could be involve d in the decrease of lipoprotein Lipase activity in the parametrial wh ite adipose tissue.