Pharmacological assessment of adrenergic receptors in human varicose veins

Background. Experiments were to characterize pharmacologically adrenergic receptors in human varicose veins to the natural transmitter norepinephrine and to an extract of Ruscus. Methods. Greater saphenous veins and varicose tributaries from patients undergoing elective surgery for primary varicose disease and portions of greater saphenous veins from patients undergoing peripheral arterial reconstruction (control) were suspended for the measurement of isometric force in organ chambers. Concentration response curves were obtained to norepinephrine or the extract of Ruscus aculeatus in the absence and presence of selective antagonists of alpha, and alpha₂ adrenergic receptors. Results. Norepinephrine and Ruscus extract caused concentration-dependent contractions in all veins. Contractions to norepinephrine were greater in control veins than in varicose tributaries. Contractions to the extract were greater in varicose tributaries than in greater saphenous veins from varicose patients. Contractions to norepinephrine were reduced similarly by alpha₁ and alpha₂-adrenergic agonists in control and varicose veins but to a greater extent by alpha₂-blockade in greater saphenous veins from varicose patients. Contractions to Ruscus extract were not reduced by alpha-adrenergic blockade in control veins but were reduced by alpha₂-adrenergic blockade in varicose veins. Conclusions. These results suggest a differential distribution of alpha adrenergic receptors on greater saphenous veins from non-varicose patients compared to those with primary varicose disease. Venotropic agents from plant extract probably exert effects by way of multiple receptor and non-receptor mediated events.