Inhibitory effect of two steroids on the accumulation of [3H]metaraminol by rat tissues in vivo.

The present experiments were designed to investigate the effect of methylprednisolone and dexamethasone on tritiated metaraminol uptake in the whole animal. Rats received i.p. injections of methylprednisolone (5, 10 and 20 mg kg-1) or dexamethasone (1, 2 and 4 mg kg-1) on each of 3 consecutive days. Under light ether anaesthesia 5 min before death the rats received radioactive metaraminol (3 microgram kg-1) via the femoral vein. Samples of various organs were removed and prepared for scintillation counting. The highest radioactivity was observed in the lungs and heart, followed by the kidney medulla, aorta, kidney cortex and submaxillary gland. Both steroids significantly inhibited uptake of metaraminol in the tissues examined. Dexamethasone seems to be more potent that methylprednisolone. It is concluded that these steroids may modify the uptake mechanism responsible for inactivation of the sympathomimetic neurotransmitter.