Relationship between renin and intrarenal hemodynamics in hemorrhagic hypotension.
In order to investigate the possible role of the renin-angiotensin system in the regulation of intrarenal hemodynamics in hemorrhagic hypotension (HH), seven mongrel dogs have been studied under the following conditions: (a) Control, (b) HH (mean arterial pressure 70 mm Hg), and (c) HH + alpha adrenergic blockade by phenoxybenzamine (HH + POB). The following parameters were obtained for the right kidney: Intrarenal distribution of blood flow and local blood flow rates ((133)Xe washout technique); total renal blood flow (RBF) on the basis of the clearance and extraction ratio of PAH and the arterial hematocrit; plasma renin concentrations in the renal artery and vein by the method of Boucher and his associates; and renin release into the renal circulation. Alpha adrenergic blockade reverted the typical redistribution of intrarenal blood flow observed under HH. In hemorrhage, arterial and venous renin concentrations increased by a factor of 3.4 and 4.8 respectively. A further small increase was observed during HH + POB with the respective factors increasing to 4.8 and 5.3, as compared with control values. The renin release into the circulation increased by a factor of 1.2 in HH and 4.0 in HH + POB. Whereas in HH there seemed to be a relationship between increased renin concentrations or renin release, and the redistribution of blood flow, no such correlation was found during alpha-adrenergic blockade. From these observations it is concluded that renin alone is unable to maintain the typical redistribution of RBF seen during hemorrhage. Circumstantial evidence points to a permissive role of the renin-angiotensin system in the pathogenesis of the patchy cortical hypoperfusion caused by sympathoadrenergic mechanisms during hemorrhagic hypotension.
D000804:Angiotensin II / Q000494:pharmacology; D000818:Animals; D001345:Autoradiography; D004285:Dogs; D005919:Glomerular Filtration Rate; D006470:Hemorrhage / Q000503:physiopathology*; D007022:Hypotension / Q000503:physiopathology*; D007668:Kidney / Q000098:blood supply*; D007726:Krypton; D009638:Norepinephrine / Q000494:pharmacology; D010643:Phenoxybenzamine / Q000494:pharmacology; D012039:Regional Blood Flow; D012083:Renin / Q000097:blood / Q000502:physiology*
D010643:Phenoxybenzamine; D000804:Angiotensin II; D007726:Krypton; D012083:Renin; D009638:Norepinephrine