Regulation of epithelial Na+ channel (ENaC) in the salivary cell line SMG-C6.
Glucocorticoids and mineralocorticoids modulate Na+ transport via epithelial Na+ channels (ENaC). The rat submandibular epithelial cell line, SMG-C6, expresses alpha-ENaC mRNA and protein and exhibits amiloride-sensitive Na+ transport when grown in low-serum (2.5%) defined medium, therefore, we examined the effects of altering the composition of the SMG-C6 cell growth medium on ENaC expression and function. No differences in basal or amiloride-sensitive short-circuit current (Isc) were measured across SMG-C6 monolayers grown in the absence of thyroid hormone, insulin, transferrin, or EGF. In the absence of hydrocortisone, basal and amiloride-sensitive Isc significantly decreased. Similarly, monolayers grown in 10% serum-supplemented medium had lower basal Isc and no response to amiloride. Adding hydrocortisone (1.1 microM) to either the low or 10% serum medium increased basal and amiloride-sensitive Isc, which was blocked by RU486, the glucocorticoid and progesterone receptor antagonist. Aldosterone also induced an increase in alpha-ENaC expression and Na+ transport, which was also blocked by RU486 but not by the mineralocorticoid receptor antagonist spironolactone. Thus, in the SMG-C6 cell line, hydrocortisone and aldosterone increased ENaC expression and basal epithelial Na+ transport. The absence of endogenous ENaC expression in culture conditions devoid of steroids makes the properties of this cell line an excellent model for investigating pathways regulating ENaC expression and Na+ transport.
Vasquez
Margarita M
MM
Department of Pediatrics/Division of Neonatology, University of Texas Health Science Center, 7703 Floyd Curl Drive, MSC 7812, San Antonio, TX 78229-3900, USA. londonom@uthscsa.edu
Mustafa
Shamimunisa B
SB
Choudary
Ahsan
A
Seidner
Steve R
SR
Castro
Robert
R
D000450:Aldosterone / Q000494:pharmacology; D000818:Animals; D000893:Anti-Inflammatory Agents / Q000494:pharmacology; D002460:Cell Line; D062686:Epithelial Sodium Channel Blockers; D053503:Epithelial Sodium Channels / Q000378:metabolism*; D006727:Hormone Antagonists / Q000494:pharmacology; D006854:Hydrocortisone / Q000494:pharmacology; D017136:Ion Transport / Q000187:drug effects / Q000502:physiology; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology*; D015735:Mifepristone / Q000494:pharmacology; D051381:Rats; D011980:Receptors, Progesterone / Q000037:antagonists & inhibitors / Q000378:metabolism; D012469:Salivary Glands / Q000166:cytology / Q000378:metabolism*; D012964:Sodium / Q000378:metabolism*
D000893:Anti-Inflammatory Agents; D062686:Epithelial Sodium Channel Blockers; D053503:Epithelial Sodium Channels; D006727:Hormone Antagonists; D011980:Receptors, Progesterone; D015735:Mifepristone; D000450:Aldosterone; D012964:Sodium; D006854:Hydrocortisone