title: HeLa cells express cAMP-inhibitable sodium-dependent phosphate uptake.
abstract: Receptor-mediated regulation of the sodium-phosphate symporter, and hence sodium-dependent phosphate uptake, typically relates to epithelial cells of renal origin. In this study we have characterized sodium-dependent phosphate uptake and aspects of its receptor-mediated regulation in the HeLa cell line, a cell line derived from a human epithelioid carcinoma. Phosphate uptake (greater than 90% sodium dependent; Vmax = 4.02 +/- 0.24 nmol.mg and Km = 0.11 +/- 0.02 mM phosphate at 140 mM sodium) was kinetically similar to that observed in opossum kidney cells. Incubation with vasoactive intestinal peptide (VIP) resulted in a dose-dependent (50% maximal dose of 8.8 +/- 3.6 nM) approximately fivefold increase in basal adenosine 3',5'-cyclic monophosphate (cAMP) levels (basal = 14.6 +/- 1.7 pmol.mg protein-1.15 min-1; VIP stimulated = 72.7 +/- 13.2 pmol.mg protein-1.15 min-1), as well as a dose-dependent maximal 32.6 +/- 5.5% decrease in sodium-dependent phosphate uptake (50% maximal decrease of 46.2 +/- 21.2 nM). The VIP-induced decrease in phosphate uptake was due to decrease in maximal transport (VmaxVIP = 2.78 +/- 0.16 nmol.mg protein-1.3 min-1) and not to a change in the affinity of the transporter for phosphate (KmVIP = 0.11 +/- 0.01 mM phosphate). Preincubation of HeLa cells with forskolin and cholera toxin, which stimulate adenylate cyclase, resulted in dose-dependent decreases in sodium-dependent phosphate uptake. Incubation with 8-bromo-cAMP and dibutyryl cAMP, permeant analogues of cAMP, similarly resulted in a dose-dependent decrease in sodium-dependent phosphate uptake.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Medical Service (Nephrology Section), Durham Veterans Administration Medical Center, North Carolina.
authors.forename: J R
authors.initials: JR
authors.lastname: Raymond
authors.forename: J P
authors.initials: JP
authors.lastname: Middleton
authors.forename: V W
authors.initials: VW
authors.lastname: Dennis
mesh_terms: D015124:8-Bromo Cyclic Adenosine Monophosphate / Q000494:pharmacology; D003994:Bucladesine / Q000494:pharmacology; D002772:Cholera Toxin / Q000494:pharmacology; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000378:metabolism / Q000494:pharmacology*; D006367:HeLa Cells / Q000378:metabolism*; D006801:Humans; D007700:Kinetics; D010710:Phosphates / Q000037:antagonists & inhibitors / Q000378:metabolism*; D012964:Sodium / Q000494:pharmacology*; D013997:Time Factors; D014660:Vasoactive Intestinal Peptide / Q000494:pharmacology
chemical_list: D010710:Phosphates; D005576:Colforsin; D015124:8-Bromo Cyclic Adenosine Monophosphate; D014660:Vasoactive Intestinal Peptide; D003994:Bucladesine; D002772:Cholera Toxin; D012964:Sodium; D000242:Cyclic AMP