GLYCINE-INDUCED HYPONATREMIA IN THE RAT - A MODEL OF POSTPROSTATECTOMY SYNDROME

Post-prostatectomy syndrome (PPS) is characterized by hyponatremia aft er absorption of glycine irrigant. To study the pathogenesis of this s yndrome, adult male rats with ligated ureters were infused over 15 min utes with 7.5 ml/100 g body weight of isosmotic glycine (N = 9) or man nitol (N = 9) and were compared to non-infused, ureter-ligated control s (N = 9). Immediately post-infusion, plasma sodium had decreased simi larly in glycine- and mannitol-infused animals (111 +/- 2 vs. 106 +/- 1 mmol/liter), but plasma osmolality remained at control levels in bot h groups (285 +/- 1 vs. 288 +/- 1 mOsm/kg). Two hours post-infusion, h yponatremia was stable in the mannitol group (108 +/- 1 mmol/liter), b ut in the glycine group plasma sodium increased significantly (to 120 +/- 1 mmol/liter). Plasma osmolality two hours post-infusion was maint ained in both the glycine (287 +/- 2) and mannitol (292 +/- 2) groups. Brain water in glycine-infused animals (3.90 +/- 0.01 liter/kg dry wt ) was not significantly different from the mannitol-infused group (3.8 5 +/- 0.01) and only 1.8% higher than non-infused controls (3.83 +/- 0 .02). Brain tissue glycine did not differ between the three groups. In contrast, muscle water two hours post-infusion in the glycine group w as 6% higher than mannitol-infused and 13% higher than non-infused ani mals. Muscle glycine content in the glycine group (67 +/- 4 mM/kg dry tissue) was increased when compared to both mannitol-infused (25 +/- 1 ) and non-infused (20 +/- 1) groups. Plasma ammonia and brain glutamin e were significantly increased in glycine-infused animals. In a second set of studies, infusion of 7.5 ml/100 g body weight of 1.5% (200 mmo l/liter) glycine caused only a non-significant increase in brain water . In conclusion, in a model of PPS in rats, acute hyponatremia induced by intravenous isosmotic glycine did not decrease plasma osmolality. Hyponatremia induced by isosmotic or hypoosmotic glycine caused minima l brain edema.