rats Changes in pulmonary blood flow affect vascular response to chronic hypoxia in

SUMMARY. We banded the left pulmonary arter in ratys to investigate i,n the sam e animal th,eeffect of bot h increase andd decreased flo own th lune g vasculatur aned t determino hoe w thesehemodynamic states modif thye structura l changes produce by a 2-weed k exposur to hypobarie chypoxia. In unanesthetized rats, pressures were recorded th froe maimn pulmonary artery and aortavia indwelling catheters, cardia wacs calculate outputd by th Fice k principle and, pulmonar any dsystemic vascular resistance estimated. Technetium-99m macroaggregated albumin was injected andradionuclide activity counted separatel the righ y ant oved lefrt lung as as measur oef flow A.tpostmortem, righ ant d left ventricle of ths heare t were weighe andd th lunge s injecte tdo permitanalysis of arteriogram ansd morphometri c assessmen of structura t l change in th pulmonarse yvascular bed. Flow in the left lung was reduce tod one-fifth norma inl rats with left pulmonary arterybands. In "room air" rats, pressure proxima to thl e left pulmonary artery ban andd in the right lungwas slightly higher tha in nonbanded controls bu,t not as high as in nonbanded or banded hypoxicrats. Changes in flow and pressur ien both lung osf "room air" rats with left pulmonary artery bandswere associated a wit milhd degre of extensioe onf muscl e into peripheral pulmonary arteriesnormally nonmuscular, medial hypertroph of normall y musculay r arteries and reduce, d arterialdensity. These three structural changes were presen in both lungt s of "hypoxic" rats but were muchmore severe. High i flon thw righte lung osf "hypoxic rats" with left pulmonary artery bandsworsened onl thy e degre oe f extension. Decrease and flod pressurw ien th lefe t lung of thess eanimals prevented bot the extensioh n and th mediae l hypertroph of hypoxiay bu, t not the sever ereduction in arterial density It seem. s tha tht e latter may occu ars a direct respons toe low oxygentension, whereas extensio and median l hypertroph are influencey d by altered flo anwd pressure,respectively. (Circ Re 52s : 432-441, 1983)IN previous studies, we observed that rats, during a2-week exposure to chronic hypoxia, develop a pro-gressive rise in pulmonary artery pressure associatedwith structural changes in the pulmonary vascularbed (Rabinovitch et al., 1979). The structural changesconsist of extension of muscle into peripheral arteriesnormally nonmuscular, increased medial wall thick-ness of normally muscular arteries, and reduced ar-terial density relative to alveolar. In the present study,we banded the left pulmonary artery in the rat todetermine for the first time in the same animal howincreased flow (to the right pulmonary vascular bed)and decreased flow (to the left) might alter the struc-tural remodeling of chronic hypoxia.MethodsAnimals StudiedTwenty-four adult male Sprague-Dawley rats (meanweight 336 ± 33 g) were used 1; 5 were selected randomlyto be kept in room air (room air rats) and 11 to be exposedto chronic hypobaric hypoxi (air a 38at 0 torr fo) r 2 weeks(hypoxia rats). Seve ofn the 15 room air rats had either nosurgical procedur (e2 of 7) o werr e sham operated o (f5 7):in the other eight th,e left pulmonary wa arters bandey d(room air + LPA band rats). Fiv of the e 15 hypoxia rat has deither no surgical procedure (2 of 5) or had a sham operation(3 of 5): in th othee 10r , th lefe t pulmonar way arters ybanded (hypoxi +a LPA band rats).