Methylprednisolone and adrenergic mechanisms in vascular smooth muscle.
The influence of methylprednisolone on noradrenaline-induced contractions and 3H-noradrenaline release was investigated in isolated preparations of rat aorta and portal vein. 20-200 micro M of methylprednisolone had a slight inhibitory effect on the contractions of the aorta but had no effect in the portal vein. The EC50-values noradrenaline were about 10-6 M in both vessels; methylprednisolone did not change it. The steroid changed neither spontaneous nor potassium (127 mM) induced release of 3H-noradrenaline. The potassium (127 mM) induced contracture in the portal vein had 2 phases; the second, at least partly, was produced by released intramural noradrenaline as it was depressed by reserpinization of the animal. Injection of methylprednisolone to the animal 2 h before sacrifice induced a better maintained second phase of the potassium contracture in the portal vein. Although this could mean the release of increased amounts of noradrenaline, other explanations are also possible.
D000818:Animals; D004305:Dose-Response Relationship, Drug; D008297:Male; D008775:Methylprednisolone / Q000494:pharmacology*; D009119:Muscle Contraction / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000187:drug effects*; D009638:Norepinephrine / Q000037:antagonists & inhibitors* / Q000378:metabolism / Q000494:pharmacology; D011188:Potassium / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains
D011188:Potassium; D009638:Norepinephrine; D008775:Methylprednisolone