title: Effect of transforming growth factor-alpha and parathyroid hormone-related protein on phosphate transport in renal cells.
abstract: The decrease in plasma Pi concentration and in Pi tubular reabsorption that is often encountered in malignant hypercalcemia may be ascribed to a tumor-produced parathyroid hormone (PTH)-related protein. However, tumors are known to synthesize a variety of substances, among which is transforming growth factor-alpha (TGF-alpha). We investigated the effects of TGF-alpha on Na-dependent Pi transport and on the response to PTH-related protein in cultured opossum renal epithelial cells. TGF-alpha caused a concentration- and time-dependent decrease in Na-dependent Pi transport. The inhibition of Na-dependent Pi transport was detectable by 14 h of incubation and maximal by 24 h. At that time, a concentration of 10 ng/ml of TGF-alpha produced a 35 +/- 1% inhibition. This was not associated with any change in prostaglandin production. The adenosine 3',5'-cyclic monophosphate (cAMP) response to PTH-related protein, PTH, prostaglandin E2 or forskolin, but not to pertussis toxin, was diminished in cells treated with TGF-alpha for 24 h. Similar effects on Na-dependent Pi transport and cAMP production were observed in cells incubated with epidermal growth factor. The inhibition of Na-dependent Pi transport induced by either PTH-related protein or PTH was reduced after incubation with TGF-alpha. Thus two different tumoral products, TGF-alpha and PTH-related protein, are each capable of inhibiting Na-dependent Pi transport in cultured renal cells. Both peptides may also interact and influence the effects of each other on renal Pi transport.
authors.affiliation: Department of Medicine, University Hospital of Geneva, Switzerland.
authors.forename: L
authors.initials: L
authors.lastname: Pizurki
authors.forename: R
authors.initials: R
authors.lastname: Rizzoli
authors.forename: J
authors.initials: J
authors.lastname: Caverzasio
authors.forename: J P
authors.initials: JP
authors.lastname: Bonjour
mesh_terms: D000262:Adenylyl Cyclases / Q000378:metabolism; D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D002460:Cell Line; D000242:Cyclic AMP / Q000378:metabolism; D004815:Epidermal Growth Factor / Q000494:pharmacology; D007213:Indomethacin / Q000494:pharmacology; D007668:Kidney / Q000166:cytology / Q000378:metabolism*; D008297:Male; D010281:Parathyroid Hormone / Q000494:pharmacology; D044162:Parathyroid Hormone-Related Protein; D010710:Phosphates / Q000378:metabolism*; D011506:Proteins / Q000494:pharmacology*; D051381:Rats; D012964:Sodium / Q000494:pharmacology; D016211:Transforming Growth Factor alpha / Q000494:pharmacology*
chemical_list: D010281:Parathyroid Hormone; D044162:Parathyroid Hormone-Related Protein; D010710:Phosphates; D011506:Proteins; D016211:Transforming Growth Factor alpha; D004815:Epidermal Growth Factor; D012964:Sodium; D000242:Cyclic AMP; D000262:Adenylyl Cyclases; D007213:Indomethacin