SOME EFFECTS OF A LOW-SODIUM INTAKE ON THE EXPRESSION OF P450 ALDOSTERONE SYNTHASE IN THE HAMSTER ADRENAL-CORTEX - IMMUNOBLOTTING, IMMUNOFLUORESCENT AND IMMONUGOLD ELECTRON-MICROSCOPIC STUDIES

In the current work we studied the effects of a low sodium intake on P 450 aldosterone synthase (P450aldo) in the adrenal cortex of male hams ters by Western blotting analysis. We also investigated the zonal dist ribution of P450aldo with a specific antibody using immunofluorescence and immune-gold electron microscopy. Western blotting analysis reveal ed a progressive induction of P450aldo in the adrenals of hamsters kep t on a low sodium diet, with two-, four- and eightfold increases after 2, 4 and 21 days on the diet. Immunofluorescence microscopy showed th at P450aldo was confined to the zona glomerulosa (ZG) cells. Electron microscopy showed P450aldo to be located in the mitochondria of ZG cel ls. When hamsters were maintained on a law sodium intake for 2, 11 and 21 days, P450aldo was still found only in the ZG; the ZG appeared eit her unchanged or sometimes slightly enlarged. Moreover, at days 1.1 an d 21, the intensity of the immunofluorescent signal was much stronger in the ZG of hamsters on the low sodium intake than in controls. Hence , immunocytochemistry using the colloidal-gold technique showed P450al do to be more abundant in the mitochondria of the experimental animals than in controls. To conclude, P450aldo is present only in the ZG of hamster adrenals and sodium restriction appears to induce its expressi on by stimulating production within individual ZG cells rather than by stimulating a proliferation of the ZG cells.