Figures & data
Figure 1. A typical responses of endothelium intact rat aortic rings to norepinephrine (NE) and subsequent hemoglobin (Hb). (a) In vessel rings precontracted with 50nM NE, 4μM Hb elicits an additional contraction. (b) In vessel rings pretreated with 70nM phentolamine, an alpha adrenergic antagonist, no notable contraction resulted with 50nM NE. Subsequent Hb treatment does not elicit contraction.
Figure 2. Effect of phentolamine doses on 50 nM norepinephrine (NE) and 2μM Hb mediated vessel ring contractions. Values are presented as percentage of control vessel ring tension produced by 50 nM NE (mean±1 SD, N=6 each). * P<0.05, ** P<0.01 compared with respective control vascular tension without phentolamine pretreatment.
Figure 3. A typical vessel ring responses to 37 mM KCl and 4μM Hb. Unlike NE induced contraction, pretreatment with 70nM phentolamine does not alter the KCl induced contraction. Subsequent 4μM Hb treatment elicits an additional contraction.
Figure 4. Precontraction with 50 nM norepinephrine (NE) or 37 mM KCl and vessel ring tension responses to 2 μM Hb with or without pretreatment with 70 nM phentolamine (Phentol). Values are represented as percent (mean±1 SD, N=6–7 each) of vessel ring tension responses to NE without phentolamine. * P<0.05 compared with respective pretreatment values.
Figure 5. Effect of pharmacologically induced (NE) or passively induced vascular tension (PT) on subsequent vessel ring responses to Hb. While in vessel rings precontracted with 50nM NE, 2μM Hb elicits a significant additional contraction, in vessel rings passively stretched to match the tension, 2 μM Hb did not elicit a significant contraction. Values are in mean±1 SD (N=5–6 each).
Figure 6. Effect of Ca++ on vessel ring responses to norepinephrine (NE) and Hb. (a) In the presence of 10mM EGTA, vessel ring contractile responses to NE and Hb were notably attenuated. Subsequent addition of 4mM CaCl2 restored the contraction. (b) Calcium channel blocker verapamil as high as 22μM did not alter the NE and Hb induced vessel ring contractile responses.
