The influence of fasting on the disposition of warfarin in rats

A study was undertaken to investigate the influence of fasting on the disposition of warfarin in rats. Fasting consisted of withholding solid food, but not water, immediately following warfarin (3 or 10 mg/kg s.c.) administration until sacrifice at different time intervals (3, 6, 12, 24 and 30 hours). Control animals were fed ad libitum. Total and unbound warfarin concentrations were measured in plasma and liver supernatant as well as unchanged warfarin and its metabolites in urine. The disposition of unbound warfarin was found to be markedly affected by fasting, especially at the 3 mg/kg dose: the disappearance rate of unbound warfarin from plasma was accelerated in fasted animals in contrast to that of total warfarin. In addition, unbound warfarin was cleared from plasma at a more rapid rate than total warfarin in both control and fasted animals. At the 10 mg/kg dose, the disposition of total and unbound warfarin was little affected by fasting. The concentration of unbound warfarin in the liver supernatant of fasted rats given warfarin, 3 mg/kg, was significantly increased at 6 and 24 hours of fasting. Plasma free fatty acids were significantly elevated starting at 6 hours, but no such difference was noticed with liver homogenate, except at 24 hours. The 24-hour urinary excretion of unchanged warfarin was higher in fasted rats, but fasting failed to produce any change in the excretion of warfarin metabolites. The results of the present investigation indicate that short periods of fasting influence the disposition of unbound warfarin without apparently modifying its biotransformation and further show the importance of plasma protein binding on the pharmacokinetics of warfarin.

The influence of fasting and stress on the response of rats to warfarin

A study was undertaken to investigate the influence of fasting (24 hours), epinephrine (four 0.25 mg/kg s.c. doses at hourly intervals), adrenocorticotropin (two 40 I.U. s.c. doses at 2-hour intervals) and immobilization stress (4 hours) on the response of rats to some coumarin or indanedione anticoagulants. The anticoagulants were always administered first and were followed immediately or within the next hour by the appropriate challenge. Fasting produced a significant enhancement of the antiprothrombin response to warfarin (0.5 mg/kg i.v. or 0.75-3.0 mg/kg s.c.), bishydroxycoumarin (7.5 mg/kg i.p. or 10 mg/kg s.c.) and phenindione (40 mg/kg p.o). Epinephrine and immobilization stress, but not adrenocorticotropin, similarly prolonged the prothrombin time after warfarin (0.75-3.0 mg/kg s.c.). When used in the absence of anticoagulants, all challenges had no effect on the prothrombin time. In addition, fasting did not affect the response of anticoagulated animals to vitamin K. Plasma free fatty acids were significantly increased by the various challenges. The binding constant of warfarin to undiluted plasma proteins were decreased from the control value by a factor of 1.7 and 2.0 as a result of immobilization stress and fasting, respectively. Fasting per se increased the amount of bound endogenous free fatty acids per mole of protein; the latter parameter was further increased in the presence of warfarin. The present data show that fasting and stress enhance the anticoagulant response to warfarin and suggest that this might be due to an interference of endogenous free fatty acids with binding of warfarin to plasma proteins.

Growth of bacteriophages MS2 and T7 on streptomycin-resistant mutants of Escherichia coli

Streptomycin-resistant mutants of an Hfr strain of Escherichia coli K were examined for their ability to support the growth of male-specific ribonucleic acid phage MS2 and female-specific deoxyribonucleic acid phage T7. Normally, the Hfr strain allows propagation of MS2 and is lysed by it (efficiency of plating equal to 1), whereas the same strain restricts propagation of T7 and is not lysed by it (efficiency of plating smaller than 10-7). Twenty-four isolates out of 26 independently obtained streptomycin-resistant mutants are partially or completely derestricted for propagation of T7; efficiency of plating of T7 in such strains ranges from 10-3-1. Depending on their response to plating of MS2 and T7, the streptomycin-resistant mutants can be divided into four classes. The mutants in all four classes continue to be "male" in conjugation with F- strains. Genetic analysis is presented to show that restriction of MS2, derestriction of T7, and resistance to streptomycin are the pleiotropic effects of a single mutation at the strA locus.

Protein synthesis in vitro in a system from plant mitochondria

A mitochondrial system from 48h-germinating seeds of Vigna sinensis (Linn.) Savi is capable of incorporating l-[U-(14)C]valine into proteins and is practically insensitve to cycloheximide, but highly sensitive to chloramphenicol and fusidic acid, a potent inhibitor of peptide-chain elongation factor. A system consisting of mitochondrial S-100 fraction and ribosomes from the same source and other cofactors is capable of polyphenylalanine synthesis and behaves similarly with respect to these inhibitors.

Urinary lactic dehydrogenase, alkaline phosphatase and lysozyme studies in renal disease

Urinary lactic dehydrogenase, alkaline phosphatase and lysozyme determinations were performed on 70 patients with various kidney diseases such as acute and chronic pyelonephritis, acute and chronic glomerulonephritis, idiopathic nephrotic syndrome, diabetic nephropathy, nephrosclerosis, lupus nephritis, analgesic nephropathy, gouty nephropathy, renal tuberculosis, renal lithiasis, and polycystic kidneys. Fifty-three of these patients had elevated levels of urinary lactic dehydrogenase, but this was not of any value in determining the etiology of the renal disease. Similarly, the elevation of alkaline phosphatase in 23 of the 70 had no etiological significance. Neither of these determinations was significant in indicating the degree of renal functional impairment or prognosis. The urinary lysozyme was significantly elevated in only five of the 70 patients and was of no value in indicating the presence or the seriousness of the underlying renal disease.