Characteristics and regulation of Na/Pi cotransport in a SV-40-transformed rabbit proximal tubular cell line.
An SV-40-transformed cell line of rabbit S2 proximal tubular origin (RKPC-2 cells) was used to characterize Na/P(i) cotransport. P(i) saturation experiments showed simple Michaelis-Menten behaviour and an apparent Km of 106 microM; Hill analysis of Na+ concentration dependence results in an apparent Km for Na+ of about 130 mM and suggests a stoichiometry exceeding unity. Exposure of confluent monolayers to low P(i) medium induced an increase in Na/P(i) cotransport. Incubation with 10(-9) M parathyroid hormone produced a 'paradoxical' stimulation of Na/P(i) cotransport, mimicked by pharmacological activation of protein kinase A or protein kinase C. The above regulatory events, observed on Na/P(i) cotransport, were not observed for Na(+)-dependent amino acid transport (L-proline and/or L-glutamic acid).
Müller
D
D
Institute of Physiology, University of Zürich, Switzerland.
Forgo
J
J
Murer
H
H
Biber
J
J
D000818:Animals; D001692:Biological Transport / Q000502:physiology; D002461:Cell Line, Transformed; D002472:Cell Transformation, Viral / Q000502:physiology; D004789:Enzyme Activation; D007687:Kidney Tubules, Proximal / Q000166:cytology / Q000378:metabolism*; D010281:Parathyroid Hormone / Q000494:pharmacology; D010710:Phosphates / Q000378:metabolism*; D011493:Protein Kinase C / Q000187:drug effects; D011494:Protein Kinases / Q000187:drug effects; D011817:Rabbits; D013539:Simian virus 40; D012964:Sodium / Q000378:metabolism*
D010281:Parathyroid Hormone; D010710:Phosphates; D012964:Sodium; D011494:Protein Kinases; D011493:Protein Kinase C