Phosphate excretion during 24 h of hypoxia in conscious rats.
The objective of this study was to investigate renal phosphate excretion during 24 h of hypoxia in conscious rats fed by total parenteral nutrition. Wistar rats weighing 190 g were exposed to hypoxia (inspired oxygen fraction = 0.10) or normoxia (inspired oxygen fraction = 0.21) for 24 h in a normobaric chamber. Renal clearance and hormonal studies were performed. The results showed a greater fractional excretion of phosphate (5.37 +/- 0.07%, P < 0.05) and hypophosphataemia (7.40 +/- 0.12 mg dL-1, P < 0.01) in hypoxic rats (n = 10) than in normoxic rats (n = 13; 3.50 +/- 0.37% and 8.02 +/- 0.16 mg dL-1, respectively). In addition, during hypoxia there was a significant decrease in the excretion of urinary adenosine 3',5'-cyclic monophosphate per glomerular filtrate (2.97 +/- 1.27 nmol dL-1, P < 0.005), a parameter of the renal action of parathyroid hormone, and a stable level of serum parathyroid hormone (10.2 +/- 2.6 ng mL-1) (cf. normoxia: 8.57 +/- 0.70 nmol dL-1 and 8.0 +/- 1.7 ng mL-1, respectively). However, creatinine clearance and the renal adenosine triphosphate level, both of which affect adenosine 3',5'-cyclic monophosphate excretion, were not different between the two groups. These data suggest that exposure of conscious rats to 24 h of hypoxia causes renal hyporesponsiveness to physiological levels of parathyroid hormone, which is manifested as a decrease in adenosine 3',5'-cyclic monophosphate excretion. Phosphaturia is not a direct net effect of hypoxia and secondary hypocapnia on renal phosphate transport, which is known to be regulated by parathyroid hormone through adenosine 3',5'-cyclic monophosphate.
Mimura
Y
Y
Third Department of Surgery, University of Tokyo, Japan.
D000818:Animals; D001784:Blood Gas Analysis; D003243:Consciousness; D000242:Cyclic AMP / Q000652:urine; D006706:Homeostasis / Q000502:physiology; D006854:Hydrocortisone / Q000097:blood; D000860:Hypoxia / Q000097:blood / Q000503:physiopathology / Q000652:urine*; D007773:Lactates / Q000097:blood; D019344:Lactic Acid; D008297:Male; D009638:Norepinephrine / Q000097:blood; D010281:Parathyroid Hormone / Q000097:blood / Q000502:physiology; D010289:Parenteral Nutrition, Total; D010710:Phosphates / Q000097:blood / Q000652:urine*; D051381:Rats; D017208:Rats, Wistar; D013997:Time Factors
D007773:Lactates; D010281:Parathyroid Hormone; D010710:Phosphates; D019344:Lactic Acid; D000242:Cyclic AMP; D006854:Hydrocortisone; D009638:Norepinephrine