Effect of growth and maturation in a hypoxic environment on maximum coronary flow rates of isolated rabbit hearts.
This study was designed to determine the effect of growth and maturation of rabbits in a hypoxic (H) environment on the ability to perfuse myocardium. Rabbits were raised in either a normoxic (N) (PO2 = 19.7 kPa or 149 torr) or an H environment (PO2 = 8.6 kPa or 65 +/- 3 mm Hg) and were studied at ages 5 wk (immature) and 12 wk (mature). Coronary flow (CF) was measured at baseline, during infusion of a maximally dilating concentration of adenosine (A), and at peak reactive hyperemic response to transient inflow occlusion in an isolated, non-blood-perfused heart preparation. Hearts were unloaded, paced at a constant rate (200 beats/min), and perfused at a constant inflow pressure (50 mm Hg). Regional CF was measured, using microspheres, in right ventricular, left ventricular, and atrial cardiac segments during vasodilation with A. H rabbits developed right ventricular but not left ventricular segment hypertrophy/hyperplasia. CF was greater in immature than mature hearts and higher in H than N hearts during baseline, vasodilation with A, and at peak reactive hyperemia (two-way analysis of variance, p < or = 0.05). Regional CF during vasodilation with A was greater in immature than mature hearts, in both right and left ventricular segments, and higher in H than N hearts in all cardiac segments (two-way analysis of variance, p < or = 0.05). Differences in total and regional CF between H and N hearts were present at both study ages (t test, p < or = 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)
Holmes
G
G
Pediatric Cardiology Research Lab, University of Florida College of Medicine, Gainesville 32610.
Epstein
M L
ML
D000367:Age Factors; D000818:Animals; D001783:Blood Flow Velocity; D003326:Coronary Circulation / Q000502:physiology*; D006321:Heart / Q000254:growth & development*; D000860:Hypoxia / Q000473:pathology / Q000503:physiopathology*; D066298:In Vitro Techniques; D009206:Myocardium / Q000473:pathology; D011817:Rabbits