Renal blood flow during unilateral ureteral obstruction: Effects of reduced perfusion pressure, acetylcholine, and thromboxane A2blockers in obstructed and unobstructed rat kidneys

Using a simplified avian kidney model, renal arterial perfusion pressure (RAPP) was reduced from 120 (control) to 70 mmHg (near the glomerular filtration rate autoregulatory limit) and then to 46 mmHg (below the glomerular filtration rate autoregulatory range) in kidneys with ambient or partially restricted renal portal flow. Renal blood flow (RBF) was measured with a thermal pulse decay (TPD) system, using TPD thermistor probes inserted at three locations to evaluate regional differences in RBF. The clearance (CPAH) and extraction of p-aminohippuric acid were used to calculate renal plasma flow (RPF). CPAH, RPF, and RBF values were consistently lower for kidneys with restricted portal flow than for kidneys with ambient portal flow. Reducing RAPP to 46 mmHg did not significantly reduce CPAH, RPF, or RBF in the ambient group but did significantly reduce CPAH and RPF (regressed on RAPP) in the restricted group. RBF was not significantly affected when RAPP was reduced in the restricted group, although significant regional differences in blood flow were recorded. Renal vascular resistance decreased significantly as RAPP was reduced to 46 mmHg in the ambient group, confirming the renal autoregulatory response. In separate validation studies, significant reductions in RBF were detected by the TPD system during acute obstructions of portal and/or arterial flow. Overall, the results support previous evidence that avian RBF remains constant over a wide range of RAPPs. Observations of nonuniform intrarenal distributions of portal blood flow suggest that the portal system maintains the constancy of RBF in regions with proportionately high portal-to-arterial flow ratios.

Download Full-text

Autoregulation of renal blood flow in the puppy

American Journal of Physiology-Legacy Content ◽

10.1152/ajplegacy.1975.229.4.983 ◽

1975 ◽

Vol 229 (4) ◽

pp. 983-988 ◽

Cited By ~ 43

Author(s):

PA Jose ◽

LM Slotkoff ◽

S Montgomery ◽

PL Calcagno ◽

G Eisner

Keyword(s):

Blood Flow ◽

Angiotensin Ii ◽

Renal Blood Flow ◽

Perfusion Pressure ◽

Electromagnetic Flowmeter ◽

Renin Angiotensin System ◽

Renal Perfusion ◽

Angiotensin System ◽

Group Of Seven ◽

Selective Blockade

The ability of the immature kidney to autoregulate blood flow was investigated. Renal blood flow was measured by electromagnetic flowmeter. In six puppies, selective blockade of the intrarenal effects of angiotensin II (AII) by [1-sarcosine, 8-alanine]angiotensin II (anti-AII) administered into the renal artery did not change renal blood flow. During selective renal AII blockade, intravenous AII raised perfusion pressure from 76 +/- 2 to 100 +/- 6 mmHg. Renal blood flow increased from 1.59 +/- 0.29 to 1.98 +/- 0.59 ml/g kidney per min, but returned to control levels within 40 s in spite of persistent arterial pressure elevation. In another group of seven puppies, renal blood flow remained constant despite reduction of renal perfusion pressure by aortic constriction to 60 mmHg. In two of these seven puppies intrarenal anti-AII did not abolish autoregulation. Autoregulation of renal blood flow occurs in the puppy and is not influenced by inhibition of angiotensin. The renin-angiotensin system does not appear to be involved in the normal regulation of renal blood flow in the puppy.

Download Full-text

Mechanism of intrarenal blood flow redistribution after carotid artery occlusion

AJP Renal Physiology ◽

10.1152/ajprenal.1977.232.2.f167 ◽

1977 ◽

Vol 232 (2) ◽

pp. F167-F172 ◽

Cited By ~ 1

Author(s):

E. H. Prosnitz ◽

E. J. Zambraski ◽

G. F. DiBona

Keyword(s):

Blood Flow ◽

Carotid Artery ◽

Renal Blood Flow ◽

Perfusion Pressure ◽

Renal Perfusion ◽

Artery Occlusion ◽

Carotid Artery Occlusion ◽

Outer Cortex ◽

Renal Sympathetic Nerve Activity ◽

Renal Perfusion Pressure

Bilateral carotid artery occlusion results in an increase in mean arterial pressure, an increase in renal sympathetic nerve activity, and a redistribution of renal blood flow from inner to outer cortex. To elucidate the mechanism of the renal blood flow redistribution, carotid artery occlusion was performed in anesthetized dogs with the left kidney either having renal perfusion pressure maintained constant (aortic constriction) or having alpha-adrenergic receptor blockade (phenoxybenzamine); the right kidney of the same dog served to document the normal response. When renal perfusion pressure was maintained constant, renal blood flow distribution (microspheres) was unchanged by carotid artery occlusion. In the presence of renal alpha-adrenergic receptor blockade, carotid artery occlusion elicited the usual redistribution of renal blood flow from inner to outer cortex. The redistribution of renal blood flow observed after carotid artery occlusion is mediated by the increase in renal perfusion pressure rather than the increase in renal sympathetic nerve activity.

Download Full-text