Effect of glucagon immunoneutralization on the increase in urea synthesis after hysterectomy in rats

To study the effect of glucagon immunoneutralization on postoperative changes of urea synthesis, hysterectomized rats were given one injection of a specific high titre antibody against pancreatic glucagon 24 h before operation raising the plasma glucagon binding capacity to values 10-20 times higher than the plasma glucagon concentration in control animals. Earlier studies have shown that the spontaneous rate of urea-N synthesis (UNSR) doubles 3 h after operation, and that the Vmax of the process, the capacity of urea-N synthesis (CUNS) is 50% higher than normal values 24 h after operation. Therefore, the effect of glucagon on UNSR and CUNS were investigated 3 and 24 h postoperatively, respectively. Control animals were given non immune rabbit serum. Glucagon immunoneutralization partly normalized the early increase in UNSR 3 h postoperatively (control: 4.7 +/- 0.3, hysterectomy+serum: 6.7 +/- 0.4, hysterectomy+Gluc-Ab: 5.5 +/- 0.4 mumol (min.100 g BW)-1), but had no effect on the increase of CUNS 24 h postoperatively (control: 7.9 +/- 0.3, hysterectomy+serum: 9.5 +/- 0.3, hysterectomy+Gluc-Ab: 9.8 +/- 0.5 mumol (min.100 g BW)-1). This shows that glucagon is important for the early postoperative increase in the efficacy of urea synthesis, whereas the late increase in capacity seems not to depend on hyperglucagonemia.