Alterations in temperature and tension change the electrical and mechanical activity of the smooth muscle of the guinea-pig taenia coli (Biilbring, 1955; Axelsson & Builbring, 1961), and it was therefore of interest to examine the influence of these factors on the sodium and potassium content of the tissue. Some changes in the distribution of these ions due to variations of temperature and tension have been reported previously. The immediate consequence of stretching the taenia coil was studied by Born & Biilbring (1956) who found an increased rate of loss of potassium, and a similar observation was made by Ikeda, Hayama, Chujyo & Hoshi (1958) in the smooth muscle of the intestinal wall. Cooling uterine smooth muscle was shown by Daniel & Robinson (1960) to decrease the potassium and increase the sodium content of the tissue. Similar changes were observed by Goodford & Hermansen (1961) when taeniae col were dissected and placed in an unoxygenated Ringer's saline solution at room temperature; they were largely reversed when the tissue was transferred to oxygenated Krebs's solution at 350 C.In the present work the effect has been studied of three different temperatures and a range of tensions on the total sodium and potassium content of the guinea-pig taenia coli, the rate of uptake of radioactive sodium and potassium ions, and the ratio of cell surface area to cell volume. METHODSThe procedures used were essentially those described by Goodford & Hermansen (1961). In each experiment 6-12 similar guinea-pigs were used, from each of which 7-10 pieces of taenia coli were dissected as quickly as possible. Each muscle was attached with two loops of cotton to a specially constructed 'spring balance', and was immersed in modified Krebs's solution under conditions specified in the description of results. During the first hour the tension was readjusted from time to time until it became steady at the desired value, and the pieces of muscle were then transferred to a solution containing either radioactive sodium or radioactive potassium. The composition of the solution was mm: Na+ 137, K+ 5.9, Mg2 1-2, Ca2+ 2-5, Cl-134, H2PO 1-2, HCO-15-5, D( + )-glucose 11-5, gassed with 97% O9+ 3 % CO2. It was prepared from isotonic stock solutions as described by Krebs (1950), with * 1851 Senior Student.

The effects of ip administration of methotrexate (MTX) on 3-month-old male Wistar rats were studied. We administered log doses from 125 to 2,000 mug/kg, five times per week for as long as 24 months. The massive doses were promptly lethal, and most rats receiving 500 mug or more/kg died within a few weeks. Severe hematopolietic depression and ulcerative gastrointestinal lesions were observed. Truly chronic intoxication was achieved with the lesser doses. Rats in this category developed serious liver damage, namely, varying degrees of fatty metamorphosis, necrosis, atrophy of hepatic cords, and fibrosis. Hematopoietic depletion occurred in the spleen and bone marrow. Hemosiderosis was prominent in the spleen and liver. Pulmonary lesions--chiefly emphysema, occasionally fibrosis--were found less consistently. These studies demonstrated the ability of MTX to induce lesions, most consistently hepatic, in the Wistar rat, and thus have provided an animal model to evaluate protective measures.

Serum concentrations of methotrexate (MTX) were compared in 20 patients after administration of 15 mg/mz MTX orally, intramuscularly, orally in divided doses, and/or intravenously. Higher and more sustained concentrations usually occurfed after intramuscular administration of the drug. Approximately 50% of the patients had measurable serum concentrations 24 hours after a dose, except when the drug was given intravenously. In patients continued on MTX twice a week, antimetabolic effects appeared sooner in persons with more sustained serum levels. CUMW 36: 1619-1624, 1975. VlDENCE CONTINUES TO ACCUMULATE IN E the literature demonstrating that the duration of the time that methotrexate (MTX) is present in the blood stream is an important factor in the development of the drug's an-timetabolic effect^.^^^^'^^'^^'-^^ A dose of 94 mg/lcg in mice in a single intraperitoneal dose will produce antimetabolic effects equivalent to that of 9.4 mg/kg when the dose is divided and given in five parts.' In humans, a dose of 25 mg given intravenously daily for 5 days produces antimetabolic effects equivalent to those of a 5-mg dose per day when administered by a 24-hour infusion over a 4-6-day period." Livingston and Carter" detail the wide variety of antitumor responses that have been obtained with M T X in the past, the best therapeutic results in selected tumors occurring in patients in whom the drug was given in such a way as to maintain a prolonged and relatively steady blood level of circulating drug. This has raised the question of what is the most practical way to administer this drug to maintain a blood level for a significant period of time in patients with solid tumors. Previous pharmacokinetic studies have shown that small doses of MTX are absorbed and ex

Methotrexate (MTX) inhibits the enzyme dihydrofolate reductase, which in turn limits the body's ability to perform transmethylation reactions. This study examined the hypothesis that the consequent deficiency of an important methylated compound, choline, may have contributed to the MTX-induced fatty change in the liver of W rats. Groups of rats were given MTX alone or MTX plus choline in varying dose combinations. All groups but one receiving the combined treatment showed a significantly lower triglyceride concentration in their livers and much less visible hepatocytic fat on histologic examination than did those given MTX alone. The protective effect of choline on the liver was dose related, the unaffected group having received a very small amount. Growth rate, survival, and hematopoietic depression due to MTX were unaltered by choline administration.

Because of the frequent reports of hepatic toxicity associated with long-term administration of methotrexate, a rat model was developed utilizing daily methotrexate administration. This model revealed an incidence of fatty metamorphosis of over 80 percent, atrophy and necrosis of 30 percent, and fibrosis of 10 percent. Fatty liver changes did not differ substantially from control animals in those animals receiving long-term thydroxyurea, an agent which, like methotrexate, inhibits DNA synthesis but unlike methotrexate, does not impair methylation reactions. Because choline has a lipotropic effect and because its synthesis requires methylation, an attempt was made to block the liver toxicity of methotrexate by simultaneous administration of choline. Animals so treated did not show the pathologic changes in the liver characteristic of methotrexate treatment alone. Furthermore, the accumulation of triglycerides in the liver which was characteristic of methotrexate administration was markedly reduced in those animals receiving choline. These data strongly suggest that, in the rat model, methotrexate produced liver toxicity by virtue of an effect other than inhibition of DNA synthesis; and that this toxicity can be blocked without impairing methotrexate effect on bone marrow by the administration of choline, a lipotropic agent requiring methylation for its synthesis. It is suggested that these results may have implications for human therapeutic situations involving long-term administration of methotrexate.