The metabolic pathway for the synthesis of guanidinosuccinic acid was studied in the rat. Labeled guanidinosuccinic acid was isolated from the urine of animals given L-[guanidino-14C]arginine intraperitoneally but did not appear in the urine after administration of D,L-[guanidino-14C]canavanine. Radioactive arginine and nonradioactive aspartic acid and arginine were infused in the isolated, per...

1. The rates of formation of acetoacetate and beta-hydroxybutyrate by the isolated perfused rat liver were measured under various conditions. 2. The rates found after addition of butyrate, octanoate, oleate and linoleate were about 100mumoles/hr./g. wet wt. in the liver of starved rats. These rates are much higher than those found with rat liver slices. 3. The differences between the rates give...

The induction and synthesis of metallothionein was studied in the isolated perfused rat liver, using Cd(I1) as the inducing metal. Perfusing the liver with 25 to 100 pg of Cd(I1) for 180 min revealed that the amount of Cd(I1) in metallothionein increased with the dosage of Cd(II), saturation being achieved at 75 pg. Zn(I1) in metallothionein decreased to about 60% of the level found in control ...

The uptake of free choline by isolated perfused rat liver was characterized. A saturable uptake mechanism [Ka = 0.17 +/- 0.07 mM (SD); Vmax = 0.84 +/- 0.16 mumol/min X g dry weight] and a nonsaturable mechanism (through which uptake is proportional to choline concentration in the perfusate) were identified. Most of the choline transported into hepatocytes was converted to betaine, phosphorylcho...

1. Loading the isolated perfused liver from well-fed rats with xylitol (20mm) caused a depletion of adenine nucleotides and P(i) and an accumulation of alpha-glycerophosphate. The ATP content fell to 66% of the control value after 10min and to 32% after 80min. The ADP and AMP contents also fell. After 80min 63% of the total adenine nucleotides and 59% of the P(i) had been lost. 2. The alpha-gly...

Rat liver perfused in situ briefly with a glutaraldehyde-formaldehyde mixture was homogenized in isotonic sucrose. The mitochondria, isolated from a homogenate of the perfused liver by differential centrifugation, assumed a slender and compact appearance similar to those often seen in an intact cell. The glutamic oxalacetic transaminase (GOT) activity of this mitochondrial fraction survived an ...

Hepatic phosphoenolpyruvate carboxykinase (PEPCK) is significantly increased in the hyperthyroid starved rat, and moderately decreased in the hypothyroid starved rat. As tri-iodothyronine by itself has only a small and sustained effect on the induction of this enzyme, as was previously shown in the isolated perfused organ, the effect of hypo- and hyper-thyroidism on the increase in cytosolic PE...

The short-term regulation of multidrug resistance-associated protein 3 (Mrp3/MRP3) by cAMP and PKC was investigated in sandwich-cultured rat and human hepatocytes and isolated perfused rat livers. The modulator glucagon (500 nM) and the phorbol ester PMA (0.1 muM) were utilized to increase intracellular cAMP and PKC levels, respectively. In glucagon-treated rat hepatocytes, efflux of the Mrp3 s...

The major site(s) of synthesis of plasma fibronectin is unknown. Using the isolated perfused rat liver and anti-rat fibronectin antiserum, we have measured net hepatic synthesis of fibronectin during 10-hr perfusion periods. We calculated the circulating plasma fibronectin pool of a 195-g rat with body surface area of 300 sq cm to be 3.3 mg: net hepatic synthesis of 3.75 +/- 1.0 mg/300 sq cm bo...