EFFECT OF PENTOBARBITAL-ANESTHESIA AND LAPAROTOMY ON PLASMA-RENIN ACTIVITY IN THE DOG

The effects of sodium pentobarbital and laparotomy on plasma renin activity (PRA) were examined in the dog with or without pretreatment with indomethacin. In control experiments, sodium pentobarbital (30 mg/kg, iv) caused PRA to rise from 9.98 ± 1.48 ng mL-1h-1 (mean ± SEM) during control periods to 22.49 ± 3.52 ng mL-1h-1 30 min after the administration of sodium pentobarbital (P<0.005). Sixty minutes after the induction of anesthesia, PRA was 14.21 ± 2.93 ng mL-1h-1 (0.05 < P < 0.1). In these animals, PRA was 12.92 ± 2.31 ng mL-1h-1 (P>0.1) 4 h after laparotomy. Subsequent nonhypotensive hemorrhage in these animals (7.5 mL/kg) caused PRA to rise to 21.69 ± 2.63 ng mL-1h-1 30 min after hemorrhage (P<0.005). In the animals treated with indomethacin (5 mg/kg, followed by 2.6-3.3 mg kg-1h-1), PRA was 3.60 ± 1.20 ng mL-1h-1 during control periods and 4.77 ± 1.71 ng mL-1h-1 30 min after the injection of indomethacin (P>0.1). Pentobarbital anesthesia in these animals caused PRA to rise to 15.59 ± 3.54 ng mL-1h-1 30 min after the administration of pentobarbital (P<0.005). PRA was still 9.91 ± 3.18 ng mL-1h-1 60 min after the administration of pentobarbital (P<0.01). In these animals, PRA was 12.60 ± 3.27 ng mL-1h-1 4 h after laparotomy (P>0.1). Subsequent nonhypotensive hemorrhage caused PRA to rise to 18.67 ± 2.97 ng mL-1h-1 30 min after hemorrhage (P<0.005). The data show that indomethacin does not prevent the increase in PRA produced by pentobarbital anesthesia. The data further show that laparotomy does not appear to cause an increase in PRA in the dog as in the rabbit.