Glycine-induced hyponatremia in the rat: A model of post-prostatectomy syndrome

Glycine-induced hyponatremia in the rat: A model of post-prostatectomy syndrome. Post-prostatectomy syndrome (PPS) is characterized by hyponatremia after absorption of glycine irrigant. To study the pathogenesis of this syndrome, adult male rats with ligated ureters were infused over 15 minutes with 7.5 ml/100 g body weight of isosmotic glycine (N = 9) or mannitol (N = 9) and were compared to non-infused, ureter-ligated controls (N = 9). Immediately post-infusion, plasma sodium had decreased similarly in glycine- and mannitol-infused animals (111 ± 2 vs. 106 ± 1 mmol/liter), but plasma osmolality remained at control levels in both groups (285 ± 1 vs. 288 ± 1 mOsm/kg). Two hours post-infusion, hyponatremia was stable in the mannitol group (108 ± 1 mmol/iter), but in the glycine group plasma sodium increased significantly (to 120 ± 1 mmol/liter). Plasma osmolality two hours post-infusion was maintained 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 (3.85 ± 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 was 6% higher than mannitol-infused and 13% higher than non-infused animals. 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 glutamine 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 mmol/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 minimal brain edema.