[Platelet stimulation and hypotensive action of carrageenans in the rat].

We studied the hypotensive effect of three carrageenans and of dextran sulphate in Brown Norway (BN) rats. The plasma of these BN rats is devoid of high molecular weight kininogen and poor in plasma prekallikrein. The hypotensive effect in BN rats was greatly reduced in comparison with the effects in normal rats. It was proportional to the thrombocytopenia induced by the sulphated polysaccharides and absent in rats made thrombopenic by antiplatelet serum. The hypotensive effect in BN rats was reduced by bromophenacyl bromide, mepacrine, aspirin, methysergide, promethazine and CCI 17810, and was unchanged after the administration of cobra venom factor, heparin, amino caproic acid, chloroquine, dexamethazone, lidocaine, propranolol, indomethacin, phenidone, imidazol, adenosine and cyproheptadine. The thrombopenic effect was reduced by methysergide and CCI 17810 and was not modified by bromophenacyl bromide and chloroquine.