Reference

Some molecular characteristics of methotrexate resistance in human lymphoblastoid cells

Some molecular characteristics of methotrexate resistance in human lymphoblastoid cells. Niethammer, D.; Jackson, R. C. (Dep. Kinderheilkd., Ulm, Ger.). Mol. Base Malig., Sel. Pap. Int. Symp., 90-7. Edited by: Deutsch, Erwin; Moser, Kurt; Rainer, Hugo. Thieme: Stuttgart, Ger. (English) 1976. CODEN: 36KKAT. DOCUMENT TYPE: Conference CA Section: 1 (Pharmacodynamics) The growth of W1-L2 human lymphoblastoid cells in continuous suspension culture with increasing concns. of methotrexate (I) [59-05-2] resulted in a variety of mechanisms of drug resistance. Membrane transport of folates and antifolates and the activity of folate dependent enzymes were studied. In these mutants, as in mouse leukemia cells, elevated cellular activities of dihydrofolate reductase [9002-03-3] were found; in some sublines activity increased over 200-fold. A relatively high frequency of mutants was found with impaired membrane transport of I; these mutants appeared rather late in the course of development of resistance, and in all these cases enzyme and transport mutations occurred together. Transport of 5-methyltetrahydrofolate [134-35-0], 5-formyltetrahydrofolic acid [58-05-9] and I in these cells shared a common pathway; this system was inhibited by p-chloromercuribenzene sulphonate Na salt (pCMS) [14110-97-5]. The concn. dependence of the pCMS effect was the same for I and 5-methyltetrahydrofolate transport. NaF and iodoacetate [64-69-7] did not change the rate of transport but increased the steady state cellular level of I. As in mouse tumor cells, folic acid [59-30-3] utilized a different uptake mechanism which was unaffected by pCMS. Serine hydroxymethyltransferase [9029-83-8], 10-formyltetrahydrofolate synthetase [9023-66-9] and 5,10-methylenetetrahydrofolate dehydrogenase [9029-14-5] were very active in this cell line. Thymidylate synthetase [9031-61-2] and serine hydroxymethyltransferase were both inhibited by I but these inhibitions were weak and probably did not contribute significantly to the cytotoxicity of I. Resistance involving impaired I transport during treatment of human malignant disease may be a more frequent phenomenon than in mouse leukemia, and may occur together with changes in tumor dihydrofolate reductase activity.

Effects of some diuretics and metabolic inhibitors on the sodium transport and electrical properties of the intestinal mucous membrane of the rat in situ

Effects of some diuretics and metabolic inhibitors on the sodium transport and electrical properties of the intestinal mucous membrane of the rat in situ. Shida, Masaru; Kikuchi, Shintaro (Cent. Res. Div., Takeda Chem. Ind. Ltd., Osaka, Japan). Takeda Kenkyusho Ho, 36(1-2), 53-63 (English) 1977. CODEN: TAKHAA. DOCUMENT TYPE: Journal CA Section: 1 (Pharmacodynamics) Section cross-reference(s): 13 The rat small intestine at the transitional part between the jejunum and ileum was suspended in situ in physiol. saline at 32 to 34.degree. and the transepithelial p.d. (PD), short circuit current (SCC) and sp. resistance (Re) were recorded to give the values 3 to 11 mV, 37 to 142 .mu.A/cm2 and 38 to 204 .OMEGA..cm2, resp. Addn. of 3 .times. 10-3 M NaCN to the intraluminal fluid, composed of 10 mM glucose and 145 mM NaCl, depressed the Na influx across the mucous membrane by 47%, assocd. with depression of the transepithelial PD and SCC equally by about 60%. A similar depression of the Na influx caused by addn. of 10-3 M 2,4-dinitrophenol [51-28-5] or 10-3 M iodoacetic acid [64-69-7] was accompanied by depression of the PD and ACC by about 20%. The transepithelial Re was not changed by the addn. of these metabolic inhibitors. The intraluminal administration of diuretics also depressed concn.-dependently the Na influx. The relatively similar depression of the Na influx by 35 to 45% caused by hydrochlorothiazide [58-93-5], amiloride [2609-46-3], or 10-3 M DS-511 [1,4-dimorpholino-7-phenylpyrido[3,4-d]pyridazine] [39632-88-7] was accompanied by the decrease of the SCC by 13, 11 and 24% but by the increase of the transepithelial PD was not significantly affected by any of these diuretics. Furosemide [54-31-9] (6 .times. 10-4 M) depressed the Na influx, PD, SCC and Re by 39, 32, 19 and 15%, resp. Acetazolamide [59-66-5] (10-3 M) depressed only the Na influx and SCC by 23 and 6%, resp. None of the metabolic inhibitors or the diuretics, when applied serosally in physiol. saline at the corresponding concn., nor the diuretics injected i.v. affected the Na influx or the elec. properties of the mucous membrane.