The effects of adrenergic blockade on lipoproteins using the rat as an experimental model

Adrenergic blocking drugs are known to have adverse effects on lipids and lipoproteins in man, although the mechanisms underlying these effects are unclear. In order to see whether the rat might be a suitable model to explore this issue, adrenergic blockers having differing properties with respect to receptor interaction were administered to rats orally over seven days, followed by measurement of plasma lipids and lipoproteins. Total plasma cholesterol was not significantly influenced by any of the drugs used, while triglycerides were reduced by 20% and 31% respectively with pindolol and prazosin. With respect to changes in HDL cholesterol, it was found that: (a) HDL cholesterol was significantly reduced by 8% during combined beta 1, beta 2 blockade with propranolol; (b) HDL cholesterol was not significantly changed during selective beta 1 blockade using atenolol, or during combined beta 1, beta 2 blockade and partial beta 2 stimulation using pindolol; and (c) HDL cholesterol was significantly increased during combined beta 1 blockade and beta 2 stimulation using celiprolol by 12%, or during alpha 1 blockade with prazosin by 8%. It appears that beta 2 receptor exposure or stimulation may be one of the key points in the interaction between adrenergic blockade and lipoprotein metabolism.