Spontaneous Pressure Diuresis in Conscious Rats

Authors

Janet E. Steele, University of Nebraska at Kearney
Paul H. Brand, Medical College of Ohio
Patricia J. Metting, Medical College of Ohio
Steven Loyal Britton, Medical College of Ohio

Date of this Version

1997

Document Type

Article

Comments

1997. Transactions of the Nebraska Academy of Sciences, 24: 71-80. Copyright © 1997 Steele, Brand, Metting and Britton.

Abstract

Pressure diuresis is thought to be a long-term mechanism that is essential for regulation of blood volume and arterial pressure (AP). We recently found that experimentally- induced changes in AP result in changes in urine flow (UF) within 6 seconds in anesthetized rats. To test our hypothesis that the long-term nature of pressure diuresis is the result of the cumulative sum of many short-term changes in UF occurring in response to spontaneous changes in AP, AP (via an aortic catheter) and UF (via a gravimetric method) were measured over 2 hours in 8 conscious, free-moving, chronically instrumented rats. A total of 24 2-hour recordings was obtained at a frequency of 0.1 Hz. For all trials, mean AP averaged 130.0 ± 4.1 mm Hg and mean UF averaged 25.2 ± 10.1 μl/min. A significant, positive linear relationship between UF and AP was observed in 16 (67%) of the trials, and a significant negative relationship was observed in 2 of the trials. Our results 1) demonstrate that a positive relationship between UF and AP can be observed in conscious, freemoving rats; and 2) suggest that short-term changes in UF occur in response to spontaneous changes in AP.