Effect of Hypoxia on Reactivity of Cutaneous and Mesenteric Veins of the Dog

Abstract

The reactivity of spiral strips of saphenous veins and of longitudinal strips of mesenteric veins of the dog was investigated in an organ bath. Changes in isometric tension of the preparations and variations in PO2 of the Krebs- Ringer solution were recorded. Contractions of the preparations were obtained by transmural electric stimulation (VANHOUTTE et al., 1967) or by addition of catecholamines to the bath solution. Anoxia (PO2≤ 1 mmHg) depressed the spontaneous activity exhibited by the mesenteric veins. Prolonged (30 to 60 minutes) hypoxia (PO2 = 40 mmHg) slightly depressed the frequency-response characteristics to electric stimulation in the mesenteric but not in the saphenous preparations, while prolonged anoxia (PO2≤ 1 mmHg) depressed the reactivity of both types of veins, especially as regards the lower stimulation frequencies (1 to 2 cps). A short anoxia period (5 minutes) imposed during sustained contractions, evoked by either electric stimulation (1 to 10 cps), adrenaline (5 · 10-7g/ml) or noradrenaline (5 · 10-7 to 10-6 g/ml), depressed the reactions by approximatively 30% (fig. 1). Those inhibitory effects of anoxia were greatly facilitated in glucose-free solutions. Prolonged anoxia in glucose-free solutions abolished the reactions to electric stimulation in both saphenous and mesenteric veins. The data indicate that, in isolated vein strips, the lack of oxygen decreases the myogenic activity, and to a lesser extent the reactivity to adrenergic stimulation in a way similar to what has been described for other vascular smooth muscle (FURCHGOTT, 1955; 1966; KEATINGE, 1964; LLOYD, 1967; SHIBATA and BRIGGS, 1967; DETAR and BOHR, 1968).