| Autor: |
Baines, A. D., Adamson, G., Wojciechowski, P., Pliura, D., Ho, P., Kluger, R. |
| Zdroj: |
American Journal of Physiology - Renal Physiology; April 1998, Vol. 274 Issue: 4 pF744-F752, 9p |
| Abstrakt: |
Is O2diffusivity within renal capillaries rate limiting for O2delivery to hypoxic renal tubules? Equations based on diffusion theory and developed here predict that soluble hemoglobin (Hb) increases O2diffusivity by a factor of 1 + [442 Hb%/(P50+PO2)], where P50is the partial pressure of O2at which the Hb is half saturated. To examine the effect of P50and Hb concentrations on renal function, we perfused isolated rat kidneys with Hb-P35(P50= 35 mmHg) and Hb-P11(P50= 11 mmHg). VenousPO2was lower with Hb-P11(10 ± 1 vs 16 ± 1 mmHg with arterial PO2= 35 mmHg and 28 ± 2 vs. 40 ± 2 mmHg with arterialPO2=140 mmHg;P< 0.001). Perfusate P50did not influence vascular resistance, glomerular filtration rate, O2consumption, Na reabsorption, protein excretion, or free water clearance. Percent glucose and phosphate excretion were lower with Hb-P11than with Hb-P35(P< 0.001). Urine glucose was 0.17 mmol/l with Hb-P11and 0.77 mmol/l with Hb-P35(P< 0.001). Hb-P35(2%) doubled O2delivery and lowered glucose and phosphate excretion to the level obtained with 1% Hb-P11. Thus Hb-P11delivered O2twice as effectively as Hb-P35to high-affinity sodium glucose and phosphate cotransporters in the late proximal tubule (S3 segment). Hb-P11may also have shunted O2from the outer cortex to the outer medulla and facilitated O2diffusion wherePO2was low. We conclude that diffusivity is a limiting factor in delivery of O2to hypoxic tubules. |
| Databáze: |
Supplemental Index |
| Externí odkaz: |
|
