The effect of sodium load on the development of hypertension, plasma renin and kininogen in rats with renal artery constriction

Effects of sodium load on the development of hypertension, plasma renin activity (PRA) and kininogen were studied in rats with renal artery constriction and untouched contralateral kidney. After the operation or sham-operation, 0.9% NaCl or water were given as drinking fluid. A marked hypertension (systolic pressure greater than 150 mmHg) developed in all operated rats on saline, but only in 2/3 of operated rats on water. In none of the sham-operated controls did systolic pressure exceed 150 mmHg during 7 postoperative weeks. Within the operated group on water, hypertensive rats had significantly higher PRA values than normotensive animals (P less than 0.05). Salt load slightly suppressed the PRA in sham-operated rats but not in animals with constriction renal artery, compared to sham-operated controls on water. The operated rats on salt excess had higher plasma kininogen levels than the operated normotensive rats on water (P less than 0.05), but there were no other significant differences in kininogen values between different study groups, regardless of whether blood pressure was increased or not. The results indicate that in this form of hypertension, the high blood pressure can be maintained without any increase in PRA if animals are subjected to a sodium load which sensitizes vascular beds to angiotensin. The increase in plasma kininogen, suggesting suppression of kallikrein-kinin system, is unlikely associated with the increase of blood pressure.