Inhibition of the Na+/I- symporter by harmaline and 3-amino-1-methyl-5H-pyrido(4,3-b)indole acetate in thyroid cells and membrane vesicles.
| Publication Type | Academic Article |
| Authors | Kaminsky S, Levy O, Garry M, Carrasco N |
| Journal | Eur J Biochem |
| Volume | 200 |
| Issue | 1 |
| Pagination | 203-7 |
| Date Published | 08/15/1991 |
| ISSN | 0014-2956 |
| Keywords | Carbolines, Carcinogens, Carrier Proteins, Harmaline, Membrane Proteins, Symporters |
| Abstract | Novel inhibitors of the Na+/I- symporter were identified using rat-thyroid-derived FRTL-5 cells and sealed vesicles from calf thyroid as model systems. Na(+)-dependent 125I- uptake was inhibited by the hallucinogenic drug harmaline and by a chemically related convulsive agent, 3-amino-1-methyl- 5H-pyrido(4,3-b)indole acetate (TRP-P-2). TRP-P-2 (Ki = 0.25 mM) was tenfold more effective as an inhibitor than harmaline (Ki = 4.0 mM). Inhibition by TRP-P-2 was competitive with respect to Na+ and was fully reversible. Although TRP-P-2 is a relatively low-affinity inhibitor, its affinity for the Na+ site of the Na+/I- symporter is over 100 times higher than that of Na+ (Km = 50 mM). 45Ca(2+)-efflux rates in calf thyroid membrane vesicles were not affected by TRP-P-2, indicating that membrane integrity is not disrupted by the drug. These findings show that TRP-P-2 may be a potentially useful tool for the identification and characterization of the Na+/I- symporter. |
| DOI | 10.1111/j.1432-1033.1991.tb21068.x |
| PubMed ID | 1879425 |