Ouabain-induced efflux of catecholamines and metabolites from blood vessels of normotensive and hypertensive dogs

Summary

Segments of mesenteric arteries (main trunk and branches) and of saphenous veins obtained from anaesthetized dogs were incubated during 15, 30 and 60 min in oxygenated Krebs-Henseleit medium at 37 °C, either in the absence or in the presence of ouabain (1 μmot, 10 μmol or 1 mmol/liter). Endogenous noradrenaline (NA) and dihydroxyphenylglycol (DOPEG) were determined in the tissue and in the incubation medium by HPLC-EC.

In normotensive animals, ouabain (10 μmol and 1mmol/l) increased the spontaneous efflux of NA in all vessels studied and markedly reduced the formation of DOPEG. In contrast, the lowest concentration of ouabain (1 μmol/l) had opposite effects.

The vessels of perinephritic hypertensive dogs (obtained 1 month after surgery) showed some significant differences from the vessels of normal dogs. Ouabain (1 mmol/l) had effects on the mesenteric arteries which were similar to those described above although less marked, but in the saphenous vein no such effects were observed.

It is concluded that ouabain-sensitive mechanisms play an important role in regulating the spontaneous efflux of NA and the formation of DOPEG in the adrenergic terminals of canine blood vessels; and that vessels of hypertensive animals do differ, in this aspect, from vessels of control animals.

Supported by a grant from Instituto Nacional de Investigação Científa (PmC1)