Renal responses of normal and preascitic broilers to systemic hypotension induced by unilateral pulmonary artery occlusion

During the pathophysiological progression of pulmonary hypertension syndrom e (PHS; ascites), broilers concurrently develop systemic hypotension (low m ean systemic arterial pressure) that may initiate renal retention of water and solute, contributing to fluid accumulation in the abdominal cavity (asc ites). Ln male Single Comb White Leghorns, glomerular filtration is autoreg ulated over a systemic arterial pressure range of 110 to 60 mm Hg, and corr esponding reductions in urine flow are attributed to a phenomenon known as pressure natriuresis. Acute unilateral pulmonary artery occlusion was used in the present study to reduce systemic arterial pressure toward the lower autoregulatory limit for glomerular filtration, and to evaluate kidney func tion in normal and preascitic broilers. Preascitic broilers characteristica lly exhibited lower (P less than or equal to 0.05) values for mean systemic arterial pressure (91 vs 100 mm Hg) and percentage saturation of hemoglobi n with oxygen (73 vs 84%), higher hematocrits (35 vs 30%), heavier right ve ntricles (3.44 vs 2.32 g), and higher right:total ventricular weight ratios (0.32 vs 0.24) than normal broilers. Body weights (2,445 vs 2,429 g,:respe ctively), left ventricle plus septum weights (7.16 vs: 7.19 g), and heart r ates (349 vs 341 beats/min) were similar. Preascitic broilers exhibited lar ger (P less than or equal to 0.05) dependent reductions in glomerular filtr ation, urine flow, osmolal clearance, and solute excretion and had a higher free: water clearance than normal broilers in response to pulmonary artery occlusion. The differences observed between normal and preascitic broilers demonstrate that systemic hypotension can trigger renal mechanisms contrib uting to fluid and solute retention during development of PHS.