Macroautophagic phenomena in renin granules

Effects of enalapril and sodium depletion on the renin-angiotensin system in hydronephrotic mice

The effects of enalapril and sodium depletion on renin synthesis and secretion were studied in mice with a left hydronephrotic kidney caused by unilateral ureteral ligation (UUL). In the control animals, there was no difference in plasma renin concentration between the right and left renal veins. In mice with left ureteral ligation, the renin concentration in the vein draining the hydronephrotic kidney was similar to or lower than that in the aorta under control conditions and after either stimulation with enalapril or depletion of sodium. Enalapril and sodium restriction increased plasma renin concentration, and this increase was due to secretion from the nonhydronephrotic kidney. The renin concentration per gram of kidney tissue and the mRNA for renin per gram of kidney tissue were similar in both the control and hydronephrotic kidney, and the values rose 3–4-fold in both kidneys after enalapril or sodium depletion. Immunostaining for renin confirmed these findings and indicated that renin per glomerulus was higher in the hydronephrotic kidney. Thus, removal or reduction of angiotensin II activity or depletion of sodium stimulated synthetic activity to a similar extent in the normal and hydronephrotic kidneys; however, secretion from the kidney without a macula densa (hydronephrotic) was not increased. Thus, the signals that control synthesis and secretion are different, and for these stimuli, secretion appears to require an intact macula densa.

The renin-angiotensin system in cats with chronic renal failure

The kidneys of eight male and two female cats with subacute (clinical illness 1-3 months) to chronic (clinical illness > 3 months) renal failure were examined histopathologically, electron microscopically and immunohistochemically. Semiquantitative morphometric data, obtained by measurement of the reninpositive portion of the afferent arteriole (RPP) and evaluation of the juxtaglomerular index (JGI), were compared with data from three healthy control cats. On the basis of the morphometric data, the animals with renal failure could be classified in three groups showing either a stimulated (group A), an unaltered (group B) or an inhibited (group C) renin-angiotensin system. In the three group A cats the JGI and RPP were increased (45.5 +/- 3.5%; 130 microns); in the four group B cats these values were comparable with those of the controls; in the three group C animals the JGI was decreased but the RPP was unaltered (11.7% +/- 3.2%; 56 microns). The increase in kidney renin in animals affected by chronic renal failure (CRF) may have been due to a volume depletion. Prolonged CRF seemed to result in increasing hypertrophy of renal blood vessels, leading to renal hypoxia and increasing preglomerular resistance. Reduced kidney renin status may have been caused by inhibition of renin synthesis in prolonged CRF as a result of renal ischaemia.