Collecting tubule adaptation to respiratory acidosis induced in vivo.
To examine the effects of respiratory acidosis in vivo on the adaptation of acidification in the collecting tubule, New Zealand White rabbits were exposed to a 6.7% CO2-93.3% O2 gas mixture in an environmental chamber for 0, 6, 24, or 48 h before obtaining collecting tubules for in vitro study. These collecting tubules were then perfused and bathed in vitro in identical Krebs-Ringer bicarbonate solutions. After 1 h equilibration total CO2 flux (JtCO2) was measured. The urine pH of the rabbits fell, whereas the blood bicarbonate rose as CO2 exposure time increased. In cortical collecting tubules, JtCO2 in vitro correlated with length of animal exposure to hypercarbia (y = 1.14174 + 0.1437x, r = 0.57, P = 0.002), and with the blood bicarbonate of the animal (y = 26.8471 + 0.0858x, r = 0.59, P less than 0.05). In vitro JtCO2 in medullary collecting tubules from rabbits that had been in hypercarbic atmosphere for 48 h (23.2 +/- 4.9 pmol.mm-1.min-1) did not differ from JtCO2 in control tubules (25.0 +/- 3.2 pmol.mm-1.min-1, not significant). Thus the cortical collecting tubule exhibits an adaptive increase in JtCO2 in response to hypercarbia, whereas the medullary collecting tubule does not.
Laski
M E
ME
Department of Internal Medicine, Texas Tech University Health Sciences Center, Lubbock 79430.
Kurtzman
N A
NA
D000142:Acidosis, Respiratory / Q000097:blood / Q000378:metabolism / Q000503:physiopathology*; D000222:Adaptation, Physiological; D000818:Animals; D001639:Bicarbonates / Q000097:blood; D002245:Carbon Dioxide / Q000097:blood / Q000378:metabolism; D005260:Female; D006801:Humans; D007672:Kidney Cortex; D007679:Kidney Medulla; D007684:Kidney Tubules / Q000503:physiopathology*; D007685:Kidney Tubules, Collecting / Q000378:metabolism / Q000503:physiopathology*; D010313:Partial Pressure; D010477:Perfusion; D011817:Rabbits
D001639:Bicarbonates; D002245:Carbon Dioxide