Differential effects of nephrectomy and surgery on plasma kininogens and angiotensinogen in the rat

The effects of bilateral nephrectomy or a sham operation on plasma angiotensinogen and on the different kininogens were studied in the rat. Total plasma kininogen was measured by RIA of kinins after trypsin hydrolysis. In addition, the high molecular weight (HMW) kininogen and the low molecular weight (T)-kininogen were specifically quantified by using direct RIAs. Angiotensinogen was measured by RIA of angiotensin I after exhaustion by renin. Three groups of control, nonoperated, bilaterally nephrectomized and sham-operated rats were studied in each experiment. Twenty-four hours after either a bilateral nephrectomy or a sham operation total plasma kininogen was elevated approximately 5 times when compared to control rats. Time course measurements from 0 to 48 h in 3 other groups of control, bilaterally nephrectomized and sham-operated rats demonstrated that kininogen gradually increased at 12, 24, and 48 h after the surgery and that the elevation observed in plasma kininogen appeared to be entirely due to an increase in T-kininogen levels. There was no difference in T-kininogen levels between bilaterally nephrectomized and sham-operated animals. By contrast HMW kininogen was neither influenced by surgery nor by nephrectomy. Angiotensinogen increased more than 8 times in bilaterally nephrectomized rats but displayed only little changes in sham-operated animals. During the course of this experiment it was observed that also in control animals submitted to repeated skin incision and venipuncture for blood sampling at the jugular vein, T-kininogen increased dramatically in plasma, but reached values lower than in sham-operated or bilaterally nephrectomized rats. In a third experiment performed in normal rats it was found that T-kininogen levels were more than 3 times elevated over initial values 24 h after a single blood sampling at the jugular vein. These results indicate that T-kininogen but not HMW kininogen is very sensitive to surgery, perhaps as a result of increased T-kininogen synthesis due to an inflammatory reaction. The T-kininogen might participate in the inflammatory reaction that occurs at the site of tissue injury and in the healing process. As there was no difference in T-kininogen, and in HMW kininogen levels between bilaterally nephrectomized and sham-operated rats, the kidneys do not seem to play an important role in the regulation of plasma kininogens. Angiotensinogen, HMW kininogen, and T-kininogen are therefore regulated separately after nephrectomy or surgery.