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In the present study, the effects of acute hypoxia on pulmonary and systemic blood flows and pressures were measured in four species of anesthetized reptiles with diverse lung structures and heart morphologies: varanid lizards ( Varanus exanthematicus), caimans ( Caiman latirostris), rattlesnakes ( Crotalus durissus), and tegu lizards ( Tupinambis merianae). As previously shown in turtles, hypoxia causes a reversible constriction of the pulmonary vasculature in varanids and caimans, decreasing pulmonary vascular conductance by 37 and 31%, respectively. These three species possess complex multicameral lungs, and it is likely that HPV would aid to secure ventilation-perfusion homogeneity. There was no HPV in rattlesnakes, which have structurally simple lungs where local ventilation-perfusion inhomogeneities are less likely to occur. However, tegu lizards, which also have simple unicameral lungs, did exhibit HPV, decreasing pulmonary vascular conductance by 32%, albeit at a lower threshold than varanids and caimans (6.2 kPa oxygen in inspired air vs. 8.2 and 13.9 kPa, respectively). Although these observations suggest that HPV is more pronounced in species with complex lungs and functionally divided hearts, it is also clear that other components are involved.<\/jats:p>","DOI":"10.1152\/ajpregu.00200.2005","type":"journal-article","created":{"date-parts":[[2005,6,17]],"date-time":"2005-06-17T00:37:25Z","timestamp":1118968645000},"page":"R1280-R1288","source":"Crossref","is-referenced-by-count":23,"title":["Hypoxic pulmonary vasoconstriction in reptiles: a comparative study of four species with different lung structures and pulmonary blood pressures"],"prefix":"10.1152","volume":"289","author":[{"given":"Nini","family":"Skovgaard","sequence":"first","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Augusto S.","family":"Abe","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Denis V.","family":"Andrade","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Tobias","family":"Wang","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"24","reference":[{"key":"R1","unstructured":"Andrade DV, Cruz-Neto AP, and Abe AS.Meal size and specific dynamic action in the rattlesnakeCrotalus durissus(Serpentes: Viperidae).Herpetologica53: 485\u2013493, 1997."},{"key":"R2","doi-asserted-by":"publisher","DOI":"10.1159\/000176642"},{"key":"R3","doi-asserted-by":"publisher","DOI":"10.1113\/jphysiol.1894.sp000493"},{"key":"R4","doi-asserted-by":"publisher","DOI":"10.1152\/jappl.1996.81.4.1535"},{"key":"R5","doi-asserted-by":"publisher","DOI":"10.1007\/BF00689039"},{"key":"R6","doi-asserted-by":"crossref","unstructured":"Burggren WWand Shelton G.Gas-exchange and transport during intermittent breathing in chelonian reptiles.J Exp Biol82: 75\u201392, 1979.","DOI":"10.1242\/jeb.82.1.75"},{"key":"R7","unstructured":"Burggren WWand Johansen K.Ventricular hemodynamics in the monitor lizardVaranus exanthematicus: pulmonary and systemic separation.J Exp Biol96: 343\u2013354, 1982."},{"key":"R8","doi-asserted-by":"publisher","DOI":"10.1152\/ajpregu.1992.263.2.R400"},{"key":"R9","doi-asserted-by":"publisher","DOI":"10.1210\/endo-126-2-985"},{"key":"R10","doi-asserted-by":"crossref","unstructured":"Crossley DA, Altimiras J, and Wang T.Hypoxia elicits pulmonary vasoconstriction in anaesthetized turtles.J Exp Biol201: 3367\u20133375, 1998.","DOI":"10.1242\/jeb.201.24.3367"},{"key":"R11","doi-asserted-by":"publisher","DOI":"10.1002\/(SICI)1097-010X(20000601)286:7<683::AID-JEZ2>3.0.CO;2-4"},{"key":"R12","doi-asserted-by":"publisher","DOI":"10.1152\/physrev.1984.64.2.544"},{"key":"R13","doi-asserted-by":"publisher","DOI":"10.1152\/ajpheart.1980.238.6.H761"},{"key":"R14","doi-asserted-by":"publisher","DOI":"10.1152\/ajpregu.1984.247.2.R402"},{"key":"R15","doi-asserted-by":"publisher","DOI":"10.1161\/01.RES.38.4.221"},{"key":"R16","doi-asserted-by":"publisher","DOI":"10.1152\/ajpregu.00417.2004"},{"key":"R17","doi-asserted-by":"publisher","DOI":"10.1007\/s00360-005-0476-2"},{"key":"R18","unstructured":"Glass MLand Johansen K.Periodic breathing in the crocodile,Crocodylus-niloticus: consequences for the gas-exchange ratio and control of breathing.J Exp Biol208: 319\u2013325, 1979."},{"key":"R19","doi-asserted-by":"publisher","DOI":"10.1016\/0034-5687(92)90026-S"},{"key":"R20","unstructured":"Hicks JW.Cardiac shunting in reptiles: mechanism, regulation, and physiological functions. 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