RENIN SYNTHESIS BY RENAL-CELLS DURING CHR ONIC INHIBITION OF THE ANGIOTENSIN-CONVERTING ENZYME

A study was performed on renin synthesis in order to evaluate changes that occur in renal cells during angiotensin-converting enzyme chronic inhibition of Ang I in mice. Immediately after weaning, 20 CF1 mice r eceived 20 mg/l enalapril maleate in drinking water during 16 months; this group was compared with a control group. Kidney tissue was proces sed and studies using optical and electron microscope immunochemical t echniques were performed. An antirenin antibody was used, and in situ hybridization was performed to keep track of renin mRNA with a digoxyg enin-marked probe. We calculated the number of juxtaglomerular apparat us (JGA), afferent arterioles (AA) and arcuate vessels (AV) immunomark ed (IM) with antirenin and antidigoxygenin. These parameters were rend ered in JGA rates (%IMJGA) and AA (%IMAA) and AV (%IMAV) marked rates (%AV), and in the rate of JGA (%SJGA), AA (%SAA) and AV (%SAV) hybridi zation signs. Electron microscope readings were used to determine the number of gold particles per renin granule. An increase in the number of renin-producing cells was observed in animals having received enala pril chronically, beyond AJG and AA, since marking was observed in arc uate vessels. The mean %MJGA value was lower in control animals (65.6% +/- 2.4) than in treated animals (94.2% +/- 3 p < 0.05). Similar find ings occurred with %MAA: 23.6% +/- 3, (control animals) vs. 41.6% +/- 2.3, p < 0.05 (treated animals). AV were not marked in the control gro up, as they were in treated animals where %MAV was 4.4% +/- 1.6. The m RNA distribution was different in animals with RAS inhibition as compa red with control animals. Hybridization signs were observed in JGA, lo wer in control animals: %SJGA (54.8 +/- 2.58) with (84.8 +/- 3 p < 0.0 5) in treated group. In AA the control group was lower again: %SAA (19 .6 a 2.07) vs (35.2 +/- 5, p < 0.05) treated animals. In AV, signs wer e only observed in animals treated; %SAV 1.6 +/- 1.14. The amount of g old particles in renin-producing cells was different in both groups of animals. The mean number of gold particles in renin particles corresp onding to JGA in control animals was 121.8 +/- 6.90, significantly low er than in treated animals (271.8 +/- 14.6, p < 0.05). This paper show s that animals with chronically inhibited Ang II production by enalapr il increase renin synthesis, recruiting in the renal vasculature a num ber of renin-producing cells, thus recalling a condition that happens during embryological development of mammals and also in primitive vert ebrate adults.