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Role of angiotensin II in the altered renal function of congestive heart failure
Insights
Myocardial infarction in rats impairs kidney function, reducing blood flow and altering filtration. Teprotide, an ACE inhibitor, reversed these detrimental renal effects, restoring kidney hemodynamics.
Area of Science:
- Nephrology
- Cardiology
- Physiology
Background:
- Myocardial infarction (MI) significantly impacts systemic hemodynamics and organ function.
- Understanding the renal consequences of MI is crucial for managing cardiovascular disease patients.
Purpose of the Study:
- To investigate the effects of extensive myocardial infarction on glomerular and tubular functions in rats.
- To assess the potential of angiotensin I-converting enzyme inhibition in mitigating MI-induced renal dysfunction.
Main Methods:
- Micropuncture techniques were used to assess renal function in rats 4 weeks post-myocardial infarction.
- Hemodynamic parameters including mean arterial pressure, left ventricular end-diastolic pressure, and renal microcirculatory dynamics were measured.
- The effect of teprotide (an ACE inhibitor) on renal function was evaluated.
Main Results:
- Rats with myocardial infarction exhibited reduced mean arterial pressure and elevated left ventricular end-diastolic pressure.
- Glomerular plasma flow rate was decreased, while single nephron filtration fraction increased, indicating altered intrarenal hemodynamics.
- Elevated efferent arteriolar resistance and increased fractional proximal fluid reabsorption were observed in MI rats.
- Teprotide administration normalized or improved these altered renal parameters in MI rats.
Conclusions:
- Extensive myocardial infarction leads to significant renal hemodynamic alterations and impaired tubular function in rats.
- Angiotensin I-converting enzyme inhibition with teprotide effectively ameliorates these MI-induced renal dysfunctions.
Abstract:
Glomerular and tubule functions were assessed by micropuncture in rats with extensive myocardial infarction produced by ligation of the left coronary artery 4 weeks prior to study. When compared to sham-operated control rats, rats with myocardial infarction involving 40 +/- 4% of the left ventricular circumference had lower mean arterial pressure (96 +/- 5 vs. 122 +/- 4 mm Hg, P less than 0.005), and higher left ventricular end-diastolic pressure (24 +/- 3 vs. 5 +/- 0 mm Hg, P less than 0.001). Renal cortical microcirculatory dynamics of rats with myocardial infarction were characterized by reduced glomerular plasma flow rate (75 +/- 8 vs. 165 +/- 17 nl/min, P less than 0.005), but a proportionately lesser decline in single nephron glomerular filtration rate (28.0 +/- 2.8 vs. 41.7 +/- 3.1 nl/min, P less than 0.025), accounting for the observed rise in single nephron filtration fraction (0.38 +/- 0.02 vs. 0.25 +/- 0.02, P less than 0.005). These renal hemodynamic alterations in myocardial-infarcted rats were accompanied by a striking elevation in efferent arteriolar resistance (3.03 +/- 0.31 vs. 0.95 +/- 0.16 X 10(10) dyn X sec X cm-5, P less than 0.001). In addition, fractional proximal fluid reabsorption, assessed by end-proximal tubule fluid-to-plasma inulin concentration ratio, was elevated (2.21 +/- 0.12 vs. 1.64 +/- 0.09, P less than 0.025). The intravenous infusion of teprotide, an angiotensin I-converting enzyme inhibitor, led to the return of glomerular plasma flow rate, single nephron filtration fraction, single nephron glomerular filtration rate, efferent arteriolar resistance, and fractional proximal fluid reabsorption in myocardial-infarcted rats to, or toward, the levels found in control rats.(ABSTRACT TRUNCATED AT 250 WORDS)