title: Effects of hypertonic stress on transforming growth factor-beta activity in normal rat kidney cells.
abstract: Hypertonicity is known to modulate the expression of some genes and the action of several cytokines. We evaluated whether hypertonicity would increase the expression and/or activity of transforming growth factor-beta (TGF-beta) in normal rat kidney (NRK) cells. The bioassay for TGF-beta showed that mature TGF-beta activity was significantly increased when the cells were cultured in a hypertonic medium (500 mOsm/kg). Comparing to the isotonic medium, hypertonicity accelerated the increase in TGF-beta activity during the initial 24 hours after changing the medium. The activity was increased as the medium osmolality increased from 300 to 500 mOsm/kg. Raffinose was found to be the most effective in increasing TGF-beta activity. NaCl, glucose, and mannitol also increased TGF-beta activity. In contrast, total TGF-beta (mature and latent) activity and TGF-beta mRNA abundance did not change significantly, suggesting that hypertonicity activated TGF-beta without affecting the synthesis of TGF-beta. To determine whether collagen synthesis was increased by hypertonicity, we examined [3H] proline incorporation into NRK cells cultured in hypertonic medium. Proline incorporation increased in an osmolality-dependent manner. Raffinose was also the most effective solute at increasing the proline incorporation. Furthermore, anti-TGF-beta antibody prevented the increase in proline incorporation induced by hypertonicity. These results suggest that hypertonicity promotes the processing of latent TGF-beta to the biologically active form, resulting in the stimulation of collagen synthesis in NRK cells.
authors.affiliation: First Department of Medicine, Osaka University School of Medicine, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Sugiura
authors.forename: A
authors.initials: A
authors.lastname: Yamauchi
authors.forename: H
authors.initials: H
authors.lastname: Kitamura
authors.forename: Y
authors.initials: Y
authors.lastname: Matusoka
authors.forename: M
authors.initials: M
authors.lastname: Horio
authors.forename: E
authors.initials: E
authors.lastname: Imai
authors.forename: M
authors.initials: M
authors.lastname: Hori
mesh_terms: D000818:Animals; D000906:Antibodies / Q000494:pharmacology; D002460:Cell Line; D003094:Collagen / Q000096:biosynthesis; D005347:Fibroblasts / Q000187:drug effects / Q000378:metabolism; D006982:Hypertonic Solutions / Q000494:pharmacology*; D007668:Kidney / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D011392:Proline / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D012016:Reference Values; D013312:Stress, Physiological / Q000139:chemically induced / Q000378:metabolism*; D016212:Transforming Growth Factor beta / Q000235:genetics / Q000276:immunology / Q000378:metabolism*
chemical_list: D000906:Antibodies; D006982:Hypertonic Solutions; D012333:RNA, Messenger; D016212:Transforming Growth Factor beta; D003094:Collagen; D011392:Proline