Effect of protamine on ion conductance of upper portion of descending limb of long-looped nephron from hamsters.
To estimate the contribution of paracellular shunt pathway to the cation-selective permeability in the upper portion of the descending limb of long-looped nephron (LDLu) of hamsters, we observed the effect of protamine on salt-diffusion voltage (delta VT) and transmural resistance (RT). delta VT generated on reduction of lumen NaCl concentration was decreased from 12.0 +/- 1.4 to 7.3 +/- 1.2 mV when 100 micrograms/ml protamine were added to the lumen. Although the effect of protamine persisted after removal of the agent from the lumen, addition of 30 U/ml heparin reversed the delta VT toward the control level. The effect of protamine was dose dependent in the range from 3 to 1,000 micrograms/ml. Protamine was without effect from the bath. Studies on single salt dilution voltage revealed that 100 and 300 micrograms/ml protamine inhibited relative Na+ to Cl- permeability from 4.03 +/- 0.38 to 2.14 +/- 0.21 and from 3.75 +/- 0.37 to 1.36 +/- 0.09, respectively. Protamine markedly decreased the apparent transference number for Na+ but slightly increased the value for Cl-. Protamine also inhibited permeabilities for K+, Rb+, and Li+ relative to Cl-, indicating that the inhibitory effect of protamine was not confined to Na+ but was generalized to cations. Transmural cable analysis showed that 100 micrograms/ml protamine increased RT from 14.0 +/- 1.1 to 19.3 +/- 1.2 omega.cm2, with the effect being reversed by 30 U/ml heparin. Because the effect of protamine on RT was unaffected by ouabain in the bath, changes in RT may mainly represent those of the paracellular shunt resistance.(ABSTRACT TRUNCATED AT 250 WORDS)
Koyama
S
S
Department of Pharmacology, Jichi Medical School, Tochigi, Japan.
Yoshitomi
K
K
Imai
M
M
D000818:Animals; D001693:Biological Transport, Active / Q000187:drug effects / Q000502:physiology; D002463:Cell Membrane Permeability / Q000187:drug effects / Q000502:physiology; D002712:Chlorides / Q000378:metabolism; D006224:Cricetinae; D005260:Female; D006493:Heparin / Q000494:pharmacology; D007687:Kidney Tubules, Proximal / Q000187:drug effects* / Q000502:physiology; D008094:Lithium / Q000378:metabolism; D008297:Male; D008647:Mesocricetus; D009399:Nephrons / Q000187:drug effects / Q000502:physiology; D011188:Potassium / Q000378:metabolism; D011479:Protamines / Q000494:pharmacology*; D012413:Rubidium / Q000378:metabolism; D012964:Sodium / Q000378:metabolism*
D002712:Chlorides; D011479:Protamines; D006493:Heparin; D008094:Lithium; D012964:Sodium; D012413:Rubidium; D011188:Potassium