The effect of CdCl2 and AgNO3 pretreatment on the distribution of 110mAg+ in rat liver

The distribution of 110mAg in the elution fractions obtained from gel filtration (Sephadex G-75) of the supernatants of rat liver homogenates was studied. 110mAgNO3 was administered i.v. at the doses 0.183 and 0.912 mg Ag+ . kg-1 . b . wt.and rats were killed 30 min after the administration. Differential centrifugation of the homogenates was performed to determine 110mAg+ distribution in subcellular structures of hepatocytes. The effect of CdCl2 and AgNO3 pretreatment (2 s.c. injections of 2.5 mg . kg-1 during 48 h) was investigated and results were compared with those obtained without pretreatment. It was found that AgNO3 pretreatment does not affect 110mAg+ distribution in the elution fractions and the major part of the metal is concentrated in the high-molecular-weight protein fraction. On contrary, after CdCl2 pretreatment almost all 110mAg+ is bound in the metallothionein (MT) fraction. Differential centrifugation revealed the main portion of the metal in nuclei and cell membranes and only small amount in lysosomal supernatant. After CdCl2 pretreatment the content of 110mAg+ in supernatant considerably increases. Results confirm the affinity of silver to MT and moreover show that this metal probably does not significantly induce the MT synthesis in the liver tissue.     

Drug residue formation from ronidazole,a 5-nitroimidazole. IV. The role of the microflora

When radioactive 1-methyl-5-nitroimidazole-2-methanol carbamate, ronidazole, labeled at the 4,5-ring positions was administered orally to germ-free and conventional rats, a much larger fraction of the radioactivity was excreted in the feces of the conventional animals. Determination of the total radioactive residues present in the carcass, blood, plasma, liver, fat and kidney 5 days after dosing indicated that the carcass of the germ-free animals contained a greater quantity of residue than that of conventional rats. On the other hand, the blood of the conventional animals contained a much higher level of radioactivity than that of the germ-free animals. These results show that while the microflora influence the distribution of the drug their presence is not obligating for the formation of persistent tissue residues in rats dosed with ronidazole.     

Modalités de la contamination d'une chaine trophique marine benthique par l'argent 110 m

The distribution of^110mAg was studied in various invertebrates of a marine benthic food chain as a consequence of the immersion in contaminated seawater and/or ingestion of radioactive food. The studies on^110mAg distribution were carried out at the end of the experimental contamination (when equilibrium was reached) and during the slow stage of elimination. After contamination via the surrounding water, uptake of^110mAg occurs mainly in external organs: shells (34%) and mantle (16%) of the bivalveScrobicularia plana, exoskeleton (40%) and gills (38%) of the crabCarcinus maenas. On the contrary, contamination via food is responsible for a considerable accumulation of^110mAg in the digestive glands ofS. plana (75%) andC. maenas (56%). Moulting plays an important role in the decontamination of crabs following immersion in radioactive seawater owing to the strong contamination of the exuviae. The elimination of^110mAg from the different organs of the animals examined depends upon the mode of contamination: it is generally fast in external organs and slow in the digestive gland. Radiation doses for molluscs and crustaceans were calculated following experimental contaminations by water and food. A significant contamination of external organs is responsible for a radiation dose (in the centre of the test animals) weaker than that instigated by the accumulation of^110mAg in the digestive gland. Thus, with regard to contamination, the ambient water is important; but, from the point of view of irradiation, radioactive food is generally more important.     

Distribution and tissue retention of cesium-134 and cobalt-6o in the nile catfish clarias lazera (cuv. & val.)

The Nile catfish, Clarias lazera was found to concentrate radioactive cesium-134 and cobalt-6o from the aquatic environment. For cesium-134 the rate of uptake increased by increase of exposure time, while for cobalt-6o maximum uptake occurred after one day of exposure. The corresponding concentration factors at maximum uptake levels were 0.37 and 0.36 for cesium and cobalt respectively.The internal distribution of these radionuclides in the different tissues and organs of the fish due to uptake from the aquatic environment followed the decreasing order:For ¹³⁴Cs: muscle, bone, gills, stomach, kidneys, intestine and liver.For ⁶⁰Co: bone, muscle, gills, intestine, kidneys, stomach and liver.The internal distribution due to ingestion of these radionuclides followed nearly the same order as was found in case of uptake from the aquatic environment.     

Distribution of radioactive silver in the subcellular fractions of various tissues of the rat and its binding to low molecular weight proteins

In view of the electron microscopic evidence that silver does not penetrate cellular barriers, the distribution of radioactive silver in rat blood and subcellular fractions of liver, kidneys, spleen, and forebrain was studied. It was found that 24 h after a single intraperitoneal injection high levels of radioactivity were reached which decreased at different rates in the various tissues studied. In plasma, liver, and kidneys there was an initial rapid loss of radioactivity which was followed by a slower rate of loss. In the blood, forebrain, and spleen the loss of radioactivity was linear and somewhat slower than in the other three tissues. The cytosols of the liver and kidneys contained 60% while those of the forebrain and spleen contained 30% of the total radioactivity found in the tissue homogenates. Gel filtration on Sephadex G-75 showed that all cytosols contained two peaks of radioactivity; a high molecular weight peak which eluted just after the void volume and a low molecular weight peak. The amount of radioactivity in both peaks was, however, much lower in the chromatographic peaks of the forebrain and spleen than that found in those of the liver and kidneys. Furthermore, the spleen had a comparatively very small low molecular weight radioactive peak. In vitro experiments with liver cytosol showed similar results to those found in vivo in that the high molecular weight radioactive peak could be removed by heat. It is concluded that silver does enter cells and that silver thionein exists in the cytosols of forebrain, spleen, kidney, and liver.     

Isolation and characterization of a Mr = 110,000 glycoprotein localized to the hepatocyte bile canaliculus

A Mr = 110,000 glycoprotein, GP 110, was partially purified using wheat germ agglutinin-Sepharose affinity chromatography from a bile canalicular-enriched membrane fraction denoted N2u of rat liver. This fraction was subjected to preparative sodium dodecyl sulfate-polyacrylamide gel electrophoresis and the Mr = 110,000 polypeptide was excised and used as an immunogen in rabbits. The antisera were found to specifically recognize a Mr = 110,000 polypeptide, named GP 110, in the N2u membrane fraction. In isolated hepatocytes, GP 110 was readily accessible to cell surface iodination catalyzed by lactoperoxidase at 4 degrees C and was judged by immunoprecipitation studies to contain about 2% of total radioactivity incorporated into externally oriented proteins of the cell. Immunoprecipitated GP 110 was shown by two-dimensional polyacrylamide gel electrophoresis to migrate with an approximate pI of 4.9. Indirect immunofluorescence on frozen liver sections demonstrated that GP 110 was primarily localized in the bile canaliculus. In corroborative studies employing subcellular fractionation, it was found that GP 110 was enriched nearly 19-fold in P2, a plasma membrane fraction primarily derived from the sinusoidal domain, and 44-fold in N2u. In contrast, only low levels of GP 110 were present in endoplasmic reticulum, mitochondrial, cytosolic, and nuclear-enriched fractions of liver. The physiological function of GP 110 is as yet unknown; antisera to it did not immunoprecipitate other known bile canalicular proteins of similar molecular weights. GP 110 was found to be extensively glycosylated relative to other known membrane proteins; approximately 33% of the apparent molecular weight appear to be carbohydrate. In agreement, limited removal of N-linked carbohydrate chains indicated that there are approximately eight chains/GP 110 polypeptide. Neuraminidase treatment of GP 110 resulted in a desialylated Mr = 85,000 polypeptide suggesting that the majority of carbohydrate chains on GP 110 are of the complex type.     

Efficacy of administration of praziquantel on 2 days 2 weeks apart against Schistosoma japonicum eggs in mice

We compared a group of mice given multiple oral doses of praziquantel (PZQ) on 1 day 7 weeks after infection with Schistosoma japonicum and another group given multiple doses of PZQ over 2 days (7 and 9 weeks after infection) by examining the number of schistosome eggs and oograms in their tissues and feces. In the 1-day-protocol group (4 x 100 mg/kg x 1 day), calcified dead eggs or shells accounted for 77.4 and 70.1% of the total EPG (the total number of immature eggs, mature eggs, and calcified eggs and shells per 1 g tissue) in the liver and small intestine, respectively, 11 weeks after infection. Shells accounted for nearly half of the total EPG (54.3% liver and 46.6% small intestine). Mature eggs accounted for 8.4% (liver) and 5.1% (small intestine) of the total EPG. Only shells were found in the feces. In the 2-day-protocol group (4 x 100 mg/kg x 2 days, 2 weeks apart), dead eggs accounted for 87.2 and 89.5% of the total EPG in the liver and small intestine, respectively, 11 weeks after infection. Shells accounted for 62.5% (liver) and 75.8% (small intestine) of the total EPG. In the 2-day group, mature eggs accounted for 0.9% (liver) and 0.6% (small intestine) of the total EPG. In liver and small intestine, the EPG of immature and mature eggs in the 2-day group was significantly smaller than in the 1-day group. Especially, the tendency was clear in the case of the EPG of mature eggs. There were no schistosome eggs in the feces of the 2-day group. We found that administration of PZQ over 2 days separated by a 2-week interval was effective against S. japonicum.     

Comparison of dietary and waterborne exposure to benzo a pyrene: bioavailability,tissue disposition and CYP1A1 induction in rainbow trout Oncorhynchus mykiss

Absorption and tissue distribution of benzo\[ a ]pyrene (BaP)-derived radioactivity were studied in juvenile rainbow trout following dietary or waterborne exposure. In order to compare the bioavailability of BaP, the fish were exposed to 1.5 mCi 3H-BaP kg-1 fish, either in the diet or in the water as a 2 days static exposure. Furthermore, tissue levels of BaP-derived radioactivity bound to macromolecules in different tissues were studied in non-induced fish, and in fish induced by additional treatment with unlabelled BaP (corresponding to 5 mg kg-1 fish) in the water. Absorption and tissue distribution of 3H BaP were studied by liquid scintillation counting and whole-body autoradiography. BaPderived radioactivity bound to macromolecules in different tissues was studied by autoradiography of solvent-extracted whole-body sections. The hepatic CYP1A induction was measured as EROD activity. Exposure to unlabelled BaP resulted in a marked induction of hepatic EROD activity in rainbow trout 2 days after the start of the exposure. Significant higher concentrations of radiolabelled compound were observed in waterborne-exposed fish, in contrast to dietary-exposed fish. High concentrations of radiolabelling were observed in the gills, liver, bile, intestines, olfactory organ, kidney and the skin of the waterborne-exposed fish. In the dietary-exposed fish, high levels of radioactivity were observed in the intestines and the bile, whereas lower concentrations were present in the liver. Only traces of radioactive compound were observed in the gills. In contrast to waterborne-exposed fish, no radioactivity was detected in the olfactory organ or skin. In autoradiograms of sections extracted with a series of polar and non-polar solvents, a large fraction of radioactivity was still present in the gills, olfactory organ, liver, kidney, skin and intestinal mucosa of the waterborne-exposed fish, indicating that reactive BaP intermediates formed by CYP1A-mediated metabolism were bound to macromolecules in these tissues.     

DNA adduct formation and persistence in liver and extrahepatic tissues of northern pike (Esox lucius) following oral exposure to benzo[a]pyrene, benzo[k]fluoranthene and 7H-dibenzo[c,g]carbazole.

The formation and persistence of DNA adducts in liver, intestinal mucosa, gills and brain of juvenile northern pike (Esox lucius) following oral exposure to benzo[a]pyrene (BaP), benzo[k]fluoranthene (BkF) and 7H-dibenzo[c,g]carbazol (DBC) were analysed by 32P-postlabelling. The dosage was 25 micromol/kg body weight of each substance, administered on 5 occasions with an interval of 12-14 days. Sampling was carried out 9 days after the second treatment, and 9, 16, 33 and 78 days after the fifth treatment. Pikes were also fed with the substances singly for comparison of adduct patterns. A complex pattern of adducts was detected in all examined tissues from fish treated with the mixture. Total adduct levels were highest in intestine (347+/-17.4 nmol adducts/mol nucleotides, mean+/-SE), followed by liver (110+/-9.3), gills (69+/-6) and brain (14+/-4.2). In pike treated with BaP alone, one major adduct was detected in all examined tissues. This BaP-adduct made up approximately 50% of the total amount of adducts in the brain. Corresponding values in liver, intestine and gills were 23, 31 and 34%, respectively. One relatively weak BkF-adduct and at least 10 different DBC-adducts were detected in all analysed tissues. Total adduct level in the intestine declined to 29.4% of the maximum value 78 days after the last exposure, while there was no significant decline in adduct levels in liver, gills or brain. The results suggest that intestine is more susceptible to adduct formation than liver after oral exposure, and that adduct levels in the intestine represent ongoing or relatively recent exposure. DNA adducts in the other investigated tissues were much more persistent and may therefore accumulate during long-term exposure.     

The tissue distribution and the pattern of excretion of [14C]-13-labeled 12, 13-epoxytrichothec-9-ene in mice and rats

The distribution in the mouse tissues of 13-[14C]-12,13-epoxtrichothec-9-ene administered intravenously was determined by whole-body autoradiography and by tracing the radioactivity of the tissues oxidized in an Auto Sample Oxidizer. The appearance of the label in urine and feces was also followed by the tracer technique. The distributions of radioactivity in tissues as determined by the two methods were almost identical. On the autoradiograms of mice killed 10 min after the injection, marked blackening of the film was observed at the sites corresponding to the liver, kidney, and bladder with urine, and much less darkening at other sites. The radioactivities contained in the liver, kidney, urine and small intestine were 13.3, 2.3, 2.6 and 10.2% of the dose, respectively. The labeled toxin was rapidly excreted into urine and feces, 56.0 and 4.9% in 6 hr and 66.7 and 28.0% in 24 hr after injection, respectively. Oral administration of the labeled toxin to mother mice resulted in the appearance of radioactivity in the stomach contents of 7-day suckling mice, thus demonstrating indirectly the secretion of the toxin into the milk. An attempt to show a respiratory route of excretion in rats given the radioactive compound orally or intravenously failed to detect any radioactivity in the expired CO2 collected for 6 hr, suggesting that the 14C in the epoxy ring was intact.     

Biliary excretion of 110mAg and its kinetics in the isolated perfused liver in rats

The biliary excretion of 110mAg in rats after i.v. administration of an aqueous solution of 110mAgNO3 (4.57 micrograms; 16kBq per rat) was studied for a period of 24 hours. The maximum rate of excretion was reached in 30th minute after the metal administration and over 70% of the silver dosed was excreted during 24 hours. Using the method of isolated perfused liver it was observed that 110mAg is rapidly taken up in the liver. During the five minutes period of the perfusion less than 50% of silver administered was found in the perfusion medium. In following minutes the level of the metal in the medium remained approximately constant. It was suggested that the rate of excretion of silver and its high uptake in the liver tissue is in connection with an unusual binding of it in the bile.     

Protein phosphorylation patterns during aestivation in the land snailOtala lactea

Protein phosphorylation patterns were investigated in whole tissues and subcellular fractions of active and aestivatingOtala lactea (Müller) (Pulmonata, Helicidae). Measurement of overall protein phosphorylation showed that incorporation of³²P increased until the second day after injection and remained constant for the remaining 4 days of the time course. Comparison of tissues from aestivating and active snails on day 3 showed a decreased protein phosphorylation in aestivating snails (44% of active). No differences in total and protein-associated radioactivity for foot, mantle or haemolymph were observed. Subcellular fractionation of the hepatopancreas localized the changes to plasma membrane, microsomal, and cytosolic fractions: values for aestivating animals were reduced to 71, 37 and 58% of the corresponding active values. Separation of the individual subcellular fractions on isoelectric focusing columns revealed differences in the phosphate incorporation patterns. Plasma membrane from aestivating animal hepatopancreas had a lower overall level of incorporation and fewer radioactive peaks in the pH 7–10 region than did the plasma membrane fraction from active animals. SDS-PAGE analysis of plasma membrane fractions from active and aestivating snails showed a relative decrease in phosphorylation between 60–80 kDa and 30–40 kDa. IEF analysis of cytosolic proteins from aestivating snail hepatopancreas also showed peaks of radioactivity that were apparently shifted by 0.3 pH units toward higher pI values. Increased phosphate incorporation was observed at a peak that corresponded to the pI value for pyruvate kinase in aestivating snails but definite assignment of peaks was not possible. SDS-PAGE analysis of cytosolic proteins showed an aestivation-related decrease in relative protein phosphorylation between 30–35 kDa and 40–45 kDa. A relative increase in phosphorylation during aestivation was observed for proteins between 16–22 kDa. Overall, the data indicate that snails dramatically alter their protein phosphorylation pattern in hepatopancreas during aestivation. (Mol Cell Biochem143: 7–13, 1995)Abbreviations CY cytosol - dpm radioactive disintegrations per minute - IEF isoelectrofocusing - GP glycogen phosphorylase - MC microsomes - MT mitochondria - PAGE polyacrylamide gel electrophoresis - PKF phosphofructokinase - PK pyruvate kinase - PM plasma membrane - SDS sodium dodecyl sulphate     

The plasma transport and metabolism of retinoic acid in the rat

The transport of retinoic acid in plasma was examined in vitamin A-deficient rats maintained on small doses of radioactively labelled retinoic acid. After ultracentrifugation of serum adjusted to density 1.21, most of the radioactivity (83%) was associated with the proteins of density greater than 1.21, and not with the serum lipoproteins. Gel filtration of the labelled serum on Sephadex G-200 showed that the radioactive label was associated with protein in the molecular-weight range of serum albumin. On polyacrylamide-gel electrophoresis almost all of the recovered radioactivity migrated with serum albumin. Similar esults were obtained with serum from a normal control rat given a single oral dose of [(14)C]retinoic acid. These findings indicate that retinoic acid is transported in rat serum bound to serum albumin, and not by retinol-binding protein (the specific transport protein for plasma retinol). Several tissues and the entire remaining carcase of each rat were extracted with ethanol-acetone to determine the tissue distribution of retinoic acid and some of its metabolites. The total recover of radioactive compounds in in the entire body of the rat was about 7-9mug, representing less than 5% or 10% respectively of the total administered label in the two dosage groups studied. The results confirm that retinoic acid is not stored in any tissue. Most of the radioactive material was found in the carcase, rather than in the specific tissues analysed. Two-thirds of the radioactivity in the carcase appeared to represent unchanged retinoic acid. Of the tissues examined, the liver, kidneys and intestine had relatively high concentrations of radioactive compounds, whereas the testes and fat-pads had the lowest concentrations.     

Distribution of55Fe in juvenile adult lampreys,Petromyzon marinus L., following oral intubation of the isotope

Summary The capacity of a sanguivorous lamprey,Petromyzon marinus L., to deal with ingested iron was studied over time using autoradiography and scintillation counting of solubilized tissue samples after intubation of the oesophagus with a single dose of⁵⁵ferrous citrate. A highly efficient mechanism for absorption in the anterior intestine was recognized with 17% of the intubated radioactivity absorbed into the body after only 5 min, 66% by 3 h, and almost 80% by 21 h. Iron concentration in the epithelial cells of the anterior intestine may be a factor in restricting iron absorption during spontaneous feeding. A decline in total body radioactivity over the 15 days following iron intubation probably results from transport of the metal in the blood and release of radioiron from the mucous cells of the posterior intestine. The kidneys appear to play a smaller but still significant role in iron loss. Gradual increases in radioiron concentration (cpm g^–1 wet weight) and percent of total body radioactivity occur in the liver (2 to 26%), carcass (14 to 37%), and integument (4 to 12%) during the course of the experiment, indicating that these are the chief sites of iron storage during times of metal excess. However, eventually integument may also be a site of iron excretion. Significant fluctuations in radioiron concentration (cpm ml^–1) in whole blood during the 15 day period can be correlated with transport of the metal to sites of storage and excretion, and maybe with incorporation into haemoglobin and with erythropoietic activity. Feeding adult lampreys represent a valuable system, with both general and unique characters, for studying iron metabolism in vertebrates.     

Progesterone in the uterus. VIII. Uptake of corticosterone and incorporation of progesterone under concurrent injection of corticosterone into rat uterus

A study of the subcellular distribution of radioactivity in rat uterus after injection of labelled corticosterone showed that the radioactivity was observed in all fractions from 5 min. to 120 min. A maximum uptake was observed 10 min. after application of the labelled steroid. Competitive uptake of radioactive progesterone and unlabelled corticosterone was assayed 10 min. after injection of the hormone mixture. The ratio between radioactive progesterone and unlabelled corticosterone was 1 : 1 and 1 : 2 (moles:moles), respectively. Compared with control experiments with rats which had received radioactive progesterone alone, the results gave evidence that progesterone found in all subcellular fractions and in the total homogenate was not depressed by unlabelled corticosterone. However, unlabelled progesterone reduced the tritiated progesterone in uterine tissue. This observation demonstrates that the uptake of progesterone by rat uterus is specific.     

Comparative utilization in vivo of [U-14C] glycerol, [2-3H] glycerol, [U-14C] glucose and [1-C14] palmitate in the rat

Female rats were injected i.v. with comparable trace amounts of [U-14C] glycerol, [2-3H] glycerol, [U-14C] glucose, or [1-14C] palmitate, and killed 30 min afterwards. The radioactivity remaining in plasma at that time was maximal in animals receiving [U-14C] glucose while the appearance of radioactive lipids was higher in the [U-14C] glycerol animals than in other groups receiving hydrosoluble substrates. The carcass, more than the liver, was the tissue where the greatest proportion of radioactivity was recovered, while the greatest percentage of radioactivity appeared in the liver in the form of lipids. The values of total radioactivity found in different tissues were very similar when using either labelled glucose or glycerol but the amount recovered as lipids was much greater in the latter. The maximal proportion of radioactive lipids appeared in the fatty-acid form in the liver, carcass, and lumbar fat pads when using [U-14C] glycerol as a hydrosoluble substrate, and the highest lipidic fraction appeared in adipose tissue as labelled, esterified fatty acids. In the spleen, heart, and kidney, most of the lipidic radioactivity from any of the hydrosoluble substrates appeared as glyceride glycerol. The highest proportion of radioactivity from [1-14C] palmitate appeared in the esterified fatty acid in adipose tissue, being followed in decreasing proportion by the heart, carcass, liver, kidney, and spleen. Thus at least in part, both labelled glucose and glycerol are used throughout different routes for their conversion in vivo to lipids. A certain proportion of glycerol is directly utilized by adipose tissue. The fatty acids esterification ability differs among the tissues and does not correspond directly with the reported activities of glycerokinase, suggesting that the alpha-glycerophosphate for esterification comes mainly from glucose and not from glycerol.     

Exogenous sphingosine enters Xenopus laevis embryos grown in petri dishes and it is metabolized

Xenopus embryos of different developmental stages were exposed to 0.1 M [1-³H]sphingosine. Labeled sphingosine was quickly absorbed by Xenopus embryos. The amount of radioactivity absorbed increased with embryo age and appeared to be linearly correlated (R=0.97) to the embryo surface area. About 45% of the total radioactivity associated to the embryos was found in the skin, 22% in the intestine, 15% in the heart, 12% in the liver and 6% in the brain.A portion of [1-³H]sphingosine entered very rapidly the biosynthetic pathway of sphingolipids; after 30 min of incubation, in fact, only a small amount of free radioactive sphingosine could be detected. Sphingomyelin was the main radioactive sphingolipid synthesized; radioactive ceramide, galactosylceramide and lactosylceramide could also be recognized and quantified. On the contrary, the amount of radioactive gangliosides was hardly detectable.A portion of [1-³H]sphinogosine absorbed by Xenopus embryos (30 to 60% depending on the developmental stage) entered the catabolic pathway producing radioactive phosphoethanolamine that was recycled for the biosynthesis of radioactive phosphatidylethanolamine. This phospholipid was produced mainly in the intestine and in the skin, while sphingomyelin was the main radioactive lipid in the heart, liver and brain.     

Uptake and subcellular distribution of injected transferrin in rat liver

Radioactively labelled transferrin was injected into rats intravenously and its uptake and subcellular distribution in the liver was investigated. The amount of radioactivity in the liver remained constant from 10 min after injection. It was not influenced by asialoglycoproteins. The radioactive label was identified as asialotransferrin. After subcellular fractionation by differential and zonal sucrose density-gradient centrifugation the label was enriched in a low-density endocytic compartment showing fluorescence quenching of acridine orange and N-ethylmaleimide-sensitive ATPase activity. The data fit into a model of continuous transferrin-receptor-mediated recycling through the hepatocyte's endocytic compartment.     

Long-term distribution and metabolism of [1-14C]dolichol injected intravenously into rats

We have previously shown that [1-14C]dolichol mixed in vitro with rat serum and injected intravenously is rapidly cleared from the circulation and appears primarily in the liver. One day after injection the liver accounted for 80% of the isotope in whole animals, whereas after 130 days it represented only 50%. During the 130 days the specific radioactivity (dpm/g liver) decreased by more than 20-fold. In contrast, the spleen retained at 130 days 85% of the radioactivity initially present and its specific radioactivity decreased by only a factor of two. At this time small amounts of isotope were also found in carcass (internal organs removed), gastrointestinal tract and contents, and lungs. Trace amounts of radioactivity were extractable from testes and kidneys, while the heart and brain were essentially free of radioactivity. At all times after injection nearly all the radioactivity present in all tissues was still associated with dolichol. Only trace amounts of [1-14C]dolichyl fatty acyl ester and no [1-14C]phosphorylated derivatives of dolichol were present in the liver and spleen removed 156 days postinjection. Fractionation of liver between 1h and 93 days after injection suggested that [1-14C]dolichol becomes associated primarily with a lysosome-enriched fraction. The accumulation of [1-14C]dolichol in this and other subcellular compartments involved both an inward and outward flow of radioactivity, suggesting that deposition of dolichol in lysosomes is not a one-way terminal process.     

Rate of concentration and digestion of radioactive growth hormone preparations injected in rats,as measured by the amount and nature of radioactivity in the tissues

Summary The distribution of radioactivity in the tissues of the rat has been established after the administration of radioactive bovine growth hormone preparations.Bovine growth hormone was used either transformed in to a¹⁴C-guanidinated derivative, which was fully active, of labeled with less than 1 mole per mole of¹²⁵I.The tissue radioactivity distribution curves obtained belong to two different categories: in kidney, liver and spleen there is an early concentration which attains a maximum in 15 minutes after the injection of the hormone, and rapidly declines. In heart, skeletal muscle, pancreas, intestine, bone and fat, the radioactivity increases gradually and a steady-state is reached after 30 to 60 minutes.Kidney is the organ where the highest concentration of radioactivity occurs. However, muscle accumulates more than 60% of the initial doses after 2 hours. Very little radioactivity appears in the urine, in this period.Similar results have been obtained with pharmacological or physiological doses of the labeled hormones.Blood plasma does not degrade the injected hormone but kidney, liver and muscle rapidly produce radioactive fragments soluble in 10% trichloro-acetic acid.Dedicated to ProfessorLuis F. Leloir on the occasion of his 70^th birthday.