Angiotensin-Converting Enzyme in the Rat Kidney

Abstract

While it is known that angiotensin-converting enzyme (ACE) in the kidney is concentrated at the brush borders of the proximal tubule, the role of tubular ACE in renal physiology is not well understood. The active site of tubular ACE is exposed on the luminal surface of the brush borders and may hydrolyze peptides in the glomerular filtrate. However, a positive correlation between blood pressure and renal ACE activity was observed in spontaneously hypertensive rats, as well as in cases of ACE inhibition. Determination of ACE activity in different renal zones and immunohistochemistry demonstrated that ACE predominates in the inner cortex and that the proximal tubule in the outer cortex contains less ACE. Perhaps the inner cortex is the area responsible for alteration of renal ACE activity, since only ACE activity in the inner cortex increased following administration of the ACE inhibitor captopril. This would suggest that the induction of ACE occurs in the inner cortex. Renal ACE activity is also affected by oxidation. Thus, the activity increased when diamide, an oxidizing agent, was added to the crude extract of renal cortex and when oxygen was introduced into the extract. Therefore, tissue oxidation may be one factor affecting renal ACE activity.

Increased rat cardiac angiotensin converting enzyme activity and mRNA expression in pressure overload left ventricular hypertrophy. Effects on coronary resistance, contractility, and relaxation.

“…In the present study, we used enalaprilat which decreased the intracardiac conversion rate of angiotensin I to II to 2.1%. However, tissue angiotensin II generation might be modulated by an endogenous inhibitor of ACE (37) or angiotensin II-generating enzymes other than ACE, as well (38,39). Our findings do not exclude the presence of additional angiotensin II-generating enzymes, since enalaprilat inhibited 70%, but not all, of the angiotensin I conversion in normal rat hearts.…”

Effect of chloride and diamide on sheep kidney, lung and serum angiotensin converting enzyme

“…Though the lungs are directly exposed to oxygen , effect of O 2 or oxidationreduction system on lung ACE activity is unknown. It was reported that, ACE activity is affected by oxidation or oxygen which removes endogenous substances or inhibitors that exist in tissues (8). Sulfhydryl moiety is essential to these substances to exert inhibitory activity on ACE (9).…”