Renal vasoconstriction and transient declamp hypotension after infrarenal aortic occlusion: role of plasma purine degradation products.

To better understand renal and systemic hemodynamics associated with hindquarter ischemia produced by aortic compression, chloralose-anesthetized dogs were given phentolamine while an external clamp maintained infrarenal aortic pressure below 25 mm Hg for 45 minutes. In four sham-operated dogs, infrarenal pressure was maintained; reinforced cannulas, capable of resisting clamp compression, were placed within the aorta and the inferior vena cava. Suprarenal and infrarenal arterial pressure and renal blood flow were continuously monitored. Blood samples taken before clamp application and at 1, 3, 5, and 10 minutes after clamp removal were assayed for adenosine, inosine, xanthine, and hypoxanthine. On clamp removal suprarenal pressure immediately dropped from a preclamp pressure of 114 to 82 mm Hg but returned to preclamp values within 1 minute. Renal blood flow was significantly reduced after clamp release, reaching a nadir of 39% of preclamp flow. This reduction persisted despite a normalization of arterial pressure. Summed plasma purines were significantly elevated 1 minute after clamp removal. Sham-operated dogs showed no significant alterations in arterial pressure, renal blood flow, or plasma purine levels. This study demonstrates a significant non-alpha-adrenergic receptor-mediated reduction in renal blood flow and a coincident increase in purine degradation products after removal of an infrarenal aortic cross-clamp.