This study was designed to improve and validate methods for the accurate and consistent quantitation of angiotensin (ANG) I and II levels in rat kidney and to determine the effects on renal ANG I and II of changes in dietary sodium intake and ANG-converting enzyme (ACE) inhibition. Kidneys from pentobarbital-anesthetized rats were rapidly removed and homogenized in methanol before extraction and purification of ANG peptides by solid-phase extraction and high-performance liquid chromatography (HPLC). Recoveries of 125I-ANG I and II were greater than 80%. Reversed-phase HPLC of the partially purified methanol extract showed that greater than 75% of the ANG I- and greater than 82% of the ANG II-like immunoreactivity coeluted with ANG I and II, respectively. Dietary sodium deprivation (0.003 meq/g) and excess (1.34 meq/g) for 7 days significantly (P less than 0.01) increased and decreased renal ANG I (296 +/- 30 and 82.6 +/- 15.8 vs. 161 +/- 18 fmol/g) and ANG II (216 +/- 16 and 45.6 +/- 11.8 vs. 98 +/- 16 fmol/g) contents, respectively. Plasma ANG I and II levels showed similar changes. ACE activity was significantly upregulated by sodium deprivation in both kidney (44% increase) and plasma (30% increase). In rats fed normal chow, infusion of enalaprilat for 1 h abolished plasma ACE activity but decreased renal ACE activity by only 58%. ACE inhibition increased renal and plasma ANG I levels 2.8- and 12-fold, respectively, and decreased renal and plasma ANG II levels 75-78%.(ABSTRACT TRUNCATED AT 250 WORDS)

Renal tissue angiotensin I (Ang I) and II (Ang II) content and angiotensin converting enzyme activity were assessed in both kidneys during initial (7 days) and maintenance (25 days) phases of two-kidney, one clip hypertension in rats. At 7 and 25 days, systolic arterial pressure was 146±2 and 170±7 mm Hg, respectively. After 7 days, Ang I content of clipped kidneys was 64% and 70% higher (p< 0.001) than in nonclipped and sham-operated kidneys, respectively, when compared with levels in kidneys from sham-operated rats. In kidneys harvested 25 days after clipping one renal artery, Ang I and Ang II contents in clipped kidneys were increased 102% and 24% (p<0.01), respectively. Ang II content was also 32% higher in nonclipped kidneys. Angiotensin converting enzyme activity in nonclipped kidneys was greater (/?<0.05) than that in either clipped (46% higher) or sham-operated kidneys (57% higher). Plasma Ang I and Ang II levels were elevated at 7 days bat were not different at 25 days in clipped rats. These results demonstrate a dissociation between intrarenal and circulating levels of Ang I and Ang II and suggest that qualitatively different mechanisms may be responsible for the elevated intrarenal Ang II levels during the initial and maintenance phases of renal hypertension. (Hypertension 1992^0:763-767) KEY WORDS • renin-angjotensin system • hypertension, renal • hypertension, renovascnlar • angiotensin I • angiotensin II • kininase II T here is now considerable evidence demonstrating a close relation between the renin-angiotensin system (RAS) and the development of hypertension in the two-kidney, one clip (2K1C) Goldblatt hypertensive rat model.

How insulin traverses the continuous endothelium of the microvasculature has been poorly studied. Development of a novel assay to measure insulin transcytosis reveals an unexpected role for clathrin in insulin transendothelial transport. Insulin transcytosis is dynamin and clathrin dependent but does not require cholesterol or caveolin-1.