Mechanism underlying the changes in plasma potassium concentration during infusion of isosmotic nonelectrolyte solution.
Generally, during infusion of an isosmotic nonelectrolyte solution that permeates the cell membrane, plasma K+ concentration ([K+]pl) either does not change or it increases slightly. The mechanism underlying this [K+]pl change has not been clarified. We continuously monitored the [K+]pl and plasma Na+ concentration ([Na+]pl) for 10 min during isosmotic mannitol infusion of 1.6 ml/100 g body weight in rats with intact kidney function (intact mannitol group). In addition, in nephrectomized rats, we compared the [K+]pl change during infusion with isosmotic mannitol (which permeates the cell membrane; mannitol nephrectomized group) with that during infusion with isosmotic sucrose (which does not permeate the cell membrane; sucrose nephrectomized group) to evaluate the effect of cell volume regulation. In the intact mannitol group, [Na+]pl decreased with dilution, and [K+]pl remained relatively constant. In the sucrose nephrectomized group, [K+]pl decreased by the same percentage as [Na+]pl and gradually increased to greater than the control level. In the mannitol nephrectomized group, however, [K+]pl increased immediately after the beginning of the infusion and reached the same level as that in the sucrose nephrectomized group. To confirm that the difference in [K+]pl between the mannitol and sucrose nephrectomized groups was dependent on cell volume regulation, we investigated the changes in mean corpuscular volume of red blood cells, using a Coulter counter. This value remained constant during isosmotic sucrose infusion but increased during isosmotic mannitol infusion, returning to the original volume after the infusion. We kept [HCO3-] and pH constant throughout the experiments.(ABSTRACT TRUNCATED AT 250 WORDS)
Hirose
M
M
Kyoto Prefectural University of Medicine, Japan.
Hashimoto
S
S
Nose
H
H
Morimoto
T
T
Itoh
T
T
Natsuyama
T
T
Tanaka
Y
Y
D000818:Animals; D004912:Erythrocytes / Q000187:drug effects; D007668:Kidney / Q000502:physiology; D008297:Male; D008353:Mannitol / Q000008:administration & dosage*; D009997:Osmotic Pressure; D011188:Potassium / Q000097:blood*; D051381:Rats; D011919:Rats, Inbred Strains; D012964:Sodium / Q000097:blood; D012996:Solutions; D013395:Sucrose / Q000008:administration & dosage
D012996:Solutions; D008353:Mannitol; D013395:Sucrose; D012964:Sodium; D011188:Potassium