Evaluation of protein and peptide hydrolases in DOCA-salt hypertensive rats treated with chlorthalidone

We have reported that chlorthalidone (Chlor) prevents the development of heart hypertrophy in deoxycorticosterone acetate (DOCA)-salt hypertensive rats. The present study was carried out to determine whether Chlor (8 mg/day per animal, added to the food, for 20 days) affects kidney and heart hypertrophy in DOCA-salt (8 mg/kg, sc, twice a week) rats by causing alterations in protein and peptide hydrolysis Heart (left ventricle) and kidney enzyme activities were measured i tissue homogenates from normal-control, salt-control, DOCA-sa salt and DOCA-salt-Chlor male Wistar rats (N = 6 for each group), using azocasein as the substrate for proteolytic enzymes and specific peptides for prolylendopeptidase (PEP) and multicatalytic proteinase (MCP). The tissue weight/body weight ratio increased in parallel to elevation of blood pressure. The left ventricular muscle hypertrophy (26 per cent, P<0.05) present in the DOCA-salt hypertensive group was completely prevented by simultaneous Chlor treatment. Chlor treatment did not change the kidney hypertrophy (+79 per cent, P<0.05) observe in the salt-control (+57 per cent, P<0.05) and DOCA-salt (+74 per cent, P<0.05) groups. The hydrolysis of peptides by PEP and MCP was similar in the normal and salt-control groups. The heart PEP activity was 24 per cent higher (P<0.01) in DOCA-salt rats, whereas MCP activity was not different when compared to control groups. DOCA-salt treatment increased MCP activity in the kidney by 44 per cent while PEP activity did not differ from that of control groups. The hydrolysis of proteins by heart enzymes was increased by salt by 47 per cent. Chlor treatment restored the reduction in protein hydrolysis induced by DOCA-salt (a 21 per cent decrease, P<0.05) to a level similar to that of the normal-control group. Similarly, Chlor coadministration prevented the 30 per cent reduction in renal proteolytic activity elicited by DOCA-salt treatment. Although Chlor treatment prevented the DOCA-salt-induced reduction in protein hydrolysis, this response did not interfere with kidney hypertrophy. The mechanism by which hypertension produces hypertrophy is unclear, but our results suggest that this structural modification is not related to the activities of some peptidases, e.g. protein and peptide hydrolases.

Calpain activity of hypertrophic hearts from hypertensive rats

Heart tissue contains large amounts of the Ca²+ -activated protein-ase calpain which has been assigned a specific function in the turnover of muscle protein. The objective of the present study was to determine calpain (E.C. 3.4.22.17)-like activity in homogenates of left ventricle from hypertensive rats that developed ventricular hypertrophy. Calpain activity was assayed using heat-denaturated azocasein as a substrate in the presence of 1 mM calcium and corrected by subtraction of the Ca²+ -independent activities. Tha latter were measured in the presence of 1 mM EGTA and the products read at 440nm. Male Wistar rats (225g) were assgned to control (N=8, normal drinking water), salt (N=6, drinking water containing 1 percent NaCl) and DOCA-salt (N=6, deoxycorticosterone acetate, 8 mg/Kg, sc, twice a week for 20 days plus drinking water containing 1 percent NaCl) groups. SHR (N =6, spontaneously hypertensive rats) were also used. The calpain activity of the control group was at 3.90 ñ 0.22 mU/g wet weight tissue. Hypertension induced significant left ventricular hypertrophy in DOCA-salt rats (26 percent) and in SHR (54 percent) and a 30 percent decrease in calpain activity in both groups (P < 0.01). In the high salt load (salt group) calpain activity was also decreased, but this was not accompanied by hypertrophy...

11-Deoxycorticosterone, an inducer of a factor stimulating delta 9 desaturase activity in liver microsomes

Se estudió el efecto de la 11-desoxicorticosterona sobre la desaturación oxidativa del ácido palmítico en microsomas hepáticos de rata. La hormona incrementó en microsomas hepáticos de rata. La hormona incrementó significativamente la actividad de delta 9 desaturasa 24 h después de la inyección intraperitoneal (1 * mol/Kg peso). De la solución de lavado de microsomas hepáticos de animales tratados con hormona se obtuvo un factor proteico que, agregado a suspensiones microsomales de animales controles, fue capaz de reproducir el efecto estimulatorio sobre la delta 9 desaturasa. El factor inducido por tratamiento con desoxicorticosterona se encontró también en el citosol hepático de ratas tratadas con la hormona. Los resultados demuestran que la presencia de un hidroxilo en posición 11-ß, característico de hormonas esteroides con acción glucocorticoide, no es imprescindible para la inducción del factor proteico que regula la actividad delta 9 desaturante