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Total VO2 was decreased in both groups during severe hypoxia but limb VO2 was maintained in the beta - block group . beta - Block prevented the fall in total and limb peripheral resistance seen in severe hypoxia but did not alter the consistently more efficient utilization of total O2 delivery shown by the limb in comparison to the whole body by higher O2 extraction ratios and lower venous O2 pressure . beta - Vasodilator receptors evidently played an active part in the vasodilatation seen during severe hypoxia .
 beta - Vasodilator receptors
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: GENE 
Text: {0} 
Answer:
 beta - Vasodilator receptors