Induction of BGT-1 and amino acid system A transport activities in endothelial cells exposed to hyperosmolarity.
We studied the responses to hypertonicity of cultured endothelial cells from swine pulmonary arteries. In 0.5 osmol/kgH(2)O medium, initial cell shrinkage was followed by a regulatory volume increase (RVI), complete after 1 h, concomitant with an increase in cellular K(+) content. Then the activity of amino acid transport System A increased, accompanied by an accumulation of ninhydrin-positive solutes (NPS), reaching a peak at approximately 6 h. The subsequent decline in System A activity was paralleled by an induction of the betaine-GABA transporter (BGT-1), detected as increases of BGT-1 mRNA and of transport activity, which peaked at approximately 24 h. Inhibitors of transcription or translation prevented induction of both transport activities. The increased expression of BGT-1, which involved activation of "tonicity-responsive enhancer," was inhibited by 5 mM extracellular betaine. Cellular K(+) concentration gradually declined after the accumulation of NPS and during the induction of BGT-1. This very effective adaptation to hypertonicity suggests it has a physiological role.
Petronini
P G
PG
Dipartimento di Medicina Sperimentale, Sezione di Patologia Molecolare e Immunologia, Università degli Studi di Parma, 43100 Parma, Italy.
Alfieri
R R
RR
Losio
M N
MN
Caccamo
A E
AE
Cavazzoni
A
A
Bonelli
M A
MA
Borghetti
A F
AF
Wheeler
K P
KP
D026905:Amino Acid Transport Systems; D000818:Animals; D001622:Betaine / Q000378:metabolism; D002352:Carrier Proteins / Q000096:biosynthesis* / Q000235:genetics / Q000378:metabolism*; D002412:Cations; D002460:Cell Line; D048429:Cell Size; D002478:Cells, Cultured; D004285:Dogs; D004730:Endothelium, Vascular / Q000378:metabolism*; D050485:GABA Plasma Membrane Transport Proteins; D006982:Hypertonic Solutions; D007700:Kinetics; D009555:Ninhydrin / Q000032:analysis; D009994:Osmolar Concentration; D011188:Potassium / Q000378:metabolism; D011651:Pulmonary Artery; D012333:RNA, Messenger / Q000032:analysis; D012964:Sodium / Q000378:metabolism; D012965:Sodium Chloride / Q000008:administration & dosage; D013395:Sucrose / Q000008:administration & dosage; D013552:Swine; D005680:gamma-Aminobutyric Acid / Q000378:metabolism
D026905:Amino Acid Transport Systems; D002352:Carrier Proteins; D002412:Cations; D050485:GABA Plasma Membrane Transport Proteins; D006982:Hypertonic Solutions; D012333:RNA, Messenger; C072207:betaine plasma membrane transport proteins; D001622:Betaine; D012965:Sodium Chloride; D005680:gamma-Aminobutyric Acid; D013395:Sucrose; D012964:Sodium; D009555:Ninhydrin; D011188:Potassium