Stretch modulates amiloride sensitivity and cation selectivity of sodium channels in human B lymphocytes.
Stretch-mediated regulation of amiloride-sensitive Na+ channels was examined in Epstein-Barr virus-transformed human B lymphocytes. Cation conductances were measured using whole cell patch-clamp techniques. Stretch activation, induced by increasing the hydrostatic pressure of the bath solution, immediately and reversibly increased both inward and outward ionic conductances once a threshold of 2-5 mmH2O was reached. Ionic substitutions confirmed that stretch enhanced membrane conductivity for both Na+ and K+. Amiloride (2 microM) completely prevented the response to elevated hydrostatic pressure; however, when amiloride was applied after stretch-induced activation, the sensitivity to amiloride was dramatically decreased (inhibitor concentration that reduces whole cell current by 50% of approximately 20 microM). Evidence that the currents induced by stretch were mediated by Na+ channels was provided by the lack of response to stretch in lymphocytes from patients with Liddle's syndrome, which is caused by expression of a truncated mutant of the beta-subunit of the amiloride-sensitive Na+ channel. Pretreatment with colchicine (0.5 mM, 30 min) prevented stretch-induced activation, which shows evidence of the involvement of the cytoskeleton. These data indicate that stretch regulates the conductance of amiloride-sensitive Na+ channels in immortalized human B lymphocytes and also alters its cationic selectivity and its sensitivity to amiloride.
Achard
J M
JM
Department of Medicine, University of Alabama at Birmingham 35294-0007, USA.
Bubien
J K
JK
Benos
D J
DJ
Warnock
D G
DG
D000584:Amiloride / Q000494:pharmacology*; D001402:B-Lymphocytes / Q000187:drug effects* / Q000378:metabolism*; D002412:Cations / Q000494:pharmacology*; D003078:Colchicine / Q000494:pharmacology; D003599:Cytoskeleton / Q000502:physiology; D006801:Humans; D006874:Hydrostatic Pressure; D006973:Hypertension / Q000097:blood / Q000235:genetics / Q000473:pathology; D009994:Osmolar Concentration; D018408:Patch-Clamp Techniques; D010812:Physical Stimulation; D012083:Renin / Q000097:blood; D015222:Sodium Channels / Q000187:drug effects*
D002412:Cations; D015222:Sodium Channels; D000584:Amiloride; D012083:Renin; D003078:Colchicine