Disappearance Of Radioactivity Research Articles

Hypoglycemia Risk During Exercise After Intramuscular Injection of Insulin in Thigh in IDDM

The influence of bicycle exercise (60% of W170 [working capacity at a pulse rate of 170 beats/min]; 40 min) on the absorption of 125I-labeled fast-acting insulin (10 U; Actrapid human insulin) after intramuscular compared with subcutaneous injection in the thigh was studied on 2 consecutive days in 10 insulin-dependent diabetes mellitus (IDDM) patients. Insulin absorption was measured as disappearance of radioactivity (1st-order elimination rate constants) by continuous external monitoring and as appearance of plasma free immunoreactive insulin (IRI). Subcutaneous adipose tissue blood flow (ATBF) and skeletal muscle blood flow (MF) were measured concomitantly in the contralateral thigh with the 133Xe wash-out technique. Plasma glucose was determined intermittently. The rate constant for 125I-insulin increased during exercise from 0.46 +/- 0.08 to 1.17 +/- 0.14%/min after intramuscular injection (P less than 0.001) and from 0.31 +/- 0.05 to 0.45 +/- 0.09%/min (NS) after subcutaneous injection. The rate constant of 125I-insulin from muscle remained elevated during the 80-min recovery period. The peak plasma free-IRI value was 39 mU/L higher, the area under the IRI curve was approximately 80% greater, and the decrease in plasma glucose was approximately 2 mM greater after intramuscular injection. Whereas MF increased fivefold, ATBF did not rise significantly during exercise. The results demonstrate that intramuscular compared with subcutaneous thigh injection of insulin followed by bicycle exercise induces a marked increase in insulin absorption and a substantial fall in plasma glucose.(ABSTRACT TRUNCATED AT 250 WORDS)

The earliest site of iodination in thyroglobulin is residue number 5.

In most highly structured native proteins, as well as in thyroglobulin, the reactivity in vitro of the various tyrosyl residues toward iodine is widely different. The present work demonstrates that of nearly 70 tyrosyl residues present in rat thyroglobulin, there is one, residue number 5 from the NH2-terminal end, which has in vivo the highest affinity toward iodine, being the first one to be iodinated. In fact, when 6-(n-propyl)-2-thiouracil (PTU)-treated, iodine-deficient animals were injected with 125I and killed shortly after, we isolated from thyroid glands poorly iodinated thyroglobulin (about 1 iodine atom/thyroglobulin molecule), nearly 90% of the radioactivity of which was found as monoiodotyrosine. Although CNBr cleavage of this protein gave several fragments after gel electrophoresis only one of these, with apparent mass 27,000 Da, contained 125I. This fragment was isolated and fully characterized. Twelve cycles of automated Edman degradation were performed; the sequence found, i.e. N-I-F-E-X-Q-V-X-A-Q-X-L, indicated that the 27,000-Da fragment is the NH2 terminus of thyroglobulin. This portion of the polypeptide chain contains several tyrosyl residues which may well all be potentially involved in the early iodination of the protein. The observation that the removal of seven amino acids from the NH2 terminus is accompanied (at the fifth step) by the total disappearance of radioactivity in the resulting shortened peptide suggested that the fifth residue was the only one iodinated under these conditions. A second, more quantitative experiment was performed on thyroglobulin obtained from 6-(n-propyl)-2-thiouracil-treated animals whose death was postponed 24 h after the injection of 125I. In this case the radioactivity was found not only in a single CNBr fragment (27,000 Da) but also in other discrete species of lower molecular mass. The mixture of these peptides was subjected to seven steps of manual Edman degradation. Fragments before and after partial degradation were run in parallel on a polyacrylamide gel and the distribution of 125I compared. Besides some change in the background, the two profiles were identical except for the absence of the 27,000-Da species. This proves that all the 125I present in the 27,000-Da species was localized at the fifth residue, the same site at which the hormone molecule is preferentially synthesized under normal conditions. This result is not unexpected and is in accord with the known properties of thyroglobulin which has a polypeptide chain designed for efficient synthesis of the hormone even at low levels of iodination.

Metabolism of very low density lipoproteins in rats with isotretinoin (13-cis retinoic acid)-induced hyperlipidemia.

A significant rise in plasma triacylglycerols from the control level of 0.89 mmol/l to 1.88 mmol/l (P less than 0.001) was observed in male Sprague-Dawley rats treated for 11 days with isotretinoin (oral dosing; 10 mg/day). This rise was due to an increased level of plasma very low density lipoproteins (VLDL). When VLDL from untreated rats were labeled with 125I-labeled tyramine-cellobiose and injected intravenously into rats treated for 10 days with isotretinoin (n = 6) and in control rats (n = 6), it was found that the disappearance of radioactivity from the blood was dramatically retarded in the treated animals. The disappearance could be divided into two phases, a rapid (alpha) phase dominated the first 5 min and was followed by a slower (beta) phase. The half-life of the beta-phase increased significantly from 53 +/- 7 min in the controls, to 120 +/- 62 min after isotretinoin. VLDL prepared from isotretinoin-treated animals (n = 6) had about the same half-life in control animals (62 +/- 8 min) as had ordinary VLDL. The elimination of tracer from the blood was mainly due to uptake by the liver. The amount of radioactivity in the liver after 30 min of circulation was significantly reduced from 34 +/- 7% of injected dose in controls to 24 +/- 5% in the isotretinoin group (P = 0.013). The uptake in other organs was less than 3% per organ and was essentially unaffected by the treatment.(ABSTRACT TRUNCATED AT 250 WORDS)

Studies on the Metabolic Fate of Betamethasone Butyrate Propionate. (IV). Absorption, distribution and excretion in rats and rabbits.

3H-BBPをラットおよびウサギに0.25mg/kgで経皮(非密封法)，あるいは1mg/kgで皮下投与し，その吸収，分布，排泄について検討し，以下の結果を得た．1．軟膏またはクリームを正常皮膚動物に経皮投与した際，全身系への経皮吸収率は雄性ラットでは約3～5%，雌性ラットでは約14%，また雄性ウサギでは約14%であった．損傷皮膚雄性ラットでは約30～50%であった．2．正常皮膚動物における血液または血漿中放射能濃度の最高到達時間および最高値は雄性ラット:24時間，0.6～0.8ng/ml，雌性ラット:8時間，4.7ng/ml雄性ウサギ:13時間，3.0ng/mlであった．また，損傷皮膚雄性ラットでは5時間，8.6～15.7ng/mlであった．3．主排泄経路はラットでは糞であったが，ウサギの尿糞中排泄率の割合はほぼ同じであった．4．正常皮膚雄性ラットにおける組織内放射能濃度は，投与後8時間あるいは24時間に最高濃度を示し，肝臓，腎臓副腎，貯精嚢および膀胱に高い濃度が認められた．各組織からの消失は緩慢であり，特に血液かbの消失が遅延した．塗布部皮膚のミクロオートラジオグラムより，BBPの経皮吸収経路として付属器官を経由するルートと経表皮ルートが確認された．5．正常皮膚雄性ラットに7回反復投与した際，毎回投与後24時間における血液および組織中放射能濃度は，投与回数に伴い上昇する傾向を示した．7回投与後の血液および組織中からの放射能の消失は緩慢であったが，7回投与後の尿および糞中排泄率は単回投与群と相違が認められなかった．6．妊娠ラットに3H-BBPを皮下投与した際の全身オートラジオグラムより，胎盤通過性が確認されたものの，放射能が胎仔組織に残留する傾向は認められなかった．

Studies on the metabolic fate of azuletil sodium. (III): Absorption, distribution, metabolism and excretion after repeated oral administration to rats, transfer into the fetus and milk, and induction of the liver microsomal drug-metabolizing enzymes by the repeated oral administration to rats.

The absorption, distribution and excretion of 14C-KT1-32 were studied after repeated oral administration to male rats. Transfer of radioactivities into the fetus and milk after oral administration of 14C-KT1-32 to pregnant or lactating rats were studied. The induction of the hepatic drug-metabolizing enzymes was studied after repeated oral administration of KT1-32 to male rats.1. On day 13 and 18 of gestation, the autoradiography revealed that the radioactivity in the fetus was lower than that in the maternal blood. On day18 of gestation, the radioactivities in the fetal liver and kidney were lower than that in the maternal plasma.2. The radioactivity in the milk was lower than that in the maternal blood within 8hr after administration. The disappearance of radioactivity from the milk was slower than that from the blood.3. After repeated administration, the radioactivity in the blood reached the steady state within 24hr following the 1st administration. Cumulative excretion ratios in urine and feces reached a constant value after the 3rd administration. The radioactivities in the tissues at 24 hr reached the steady state after the 7th administration, but the disappearance of radioactivity from the tissues after the 21st administration was quite similar to that after single administartion.4. In the plasma and urine after the 21st administration, the Ml, M2 metabolites and the intact drug were detected as major components and M4, M3, M5 and M6 were found in the urine as the minor ones.5. After repeated oral administration of KT1-32 to male rats, there was no induction of the hepatic drug-metabolizing enzymes.

Kinetic Modeling of Selenium Metabolism in Nonpregnant Ewes

The kinetics of selenium metabolism in three nonpregnant ewes were studied by the intravenous injection of 75Se-sodium selenite and measurement of radioactivity responses in blood, tissues and excreta. Stable selenium measurements were also made to determine selenium intake, excretion in feces and urine, and mass of selenium in tissues. Immediately following tracer injection, there was a rapid disappearance of radioactivity from plasma reflecting the uptake of the element by the liver and blood cells. The decrease in plasma radioactivity ceased abruptly by 30-45 min, and was followed by an increase to a peak by 3-4 h and a more gradual biphasic decline thereafter. A kinetic model of selenium metabolism in the whole animal was constructed employing the SAAM/CONSAM computer program. The multiphasic response of plasma radioactivity during a physiological steady state was explained on the basis of rapid hepatic uptake of selenium and its subsequent reappearance in the circulation in protein-bound form followed by further metabolism and excretion of the element. The model provides reference parameter values for 75Se-sodium selenite kinetics in selenium-replete, mature nonpregnant ewes for comparison with the kinetics in animals whose selenium status may be altered.

A Preliminary Study of Brain Gliomas with H17E2 Monoclonal Antibody: Immunoscintigraphy and Pharmacokinetics

Ten patients with relapsing high grade brain gliomas and one patient with low grade glioma were studied with a monoclonal antibody (H17E2) against placental alkaline phosphatase. In addition 2 patients with relapsing high grade glioma were studied with a non specific antibody (4D513/2118). 1 mCi of Iodine-131-labelled H17E2 was administered intracarotidly (i.c.) in two, and intravenously (i.v.) in 9 patients. Immunoscintigrams were taken at 0, 2, 24, 48 and 72 hours. Radioactivity was monitored in blood and urine. Tumour/non-tumour ratios were estimated (max. 2.45). All high grade gliomas receiving specific antibody irrespective of the route of administration, gave a positive immunoscintigraphic pattern, increasing in intensity with time. Disappearance of radioactivity in blood was biexpontential with a long component over 30 hours. Urinary excretion of radioactivity ranged from 3.7-21.7% of administered dose/day. The patient with low grade glioma and the patients receiving non specific monoclonal antibody showed a negative pattern, a fast blood clearance and a high urinary excretion. We conclude that a) Iodine-131 labelled H17E2 proved to be stable in vivo and produced satisfactory tumour localisation and b) i.v. route was as good as i.c.

Biodistribution and excretion of 125I ioversol in conscious dogs.

Radiolabeled ioversol was injected intravenously into two male and two female beagle dogs (6.7 to 10.4 kg) at two dose levels each (0.2 and 1.0 g I/kg). Blood levels of radioactivity were monitored at 2, 5, 10, 20, 40, 60, 90, and 120 minutes and at one and two days. Urine and feces were collected in metabolism cages for two days, at the end of which the dogs were killed and organs or tissues (kidneys, liver, spleen, lungs, thyroid glands, heart, gonads, and muscle) were sampled. Radioactivity in tissues and excreta was assayed. Biexponential disappearance of radioactivity from blood was observed in three of four dogs at each dose level. Distribution half-lives averaged 2.5 to 3.5 minutes. Elimination half-lives averaged 51 to 54 minutes. Volumes of distribution averaged 25% to 27% of body weight. No organ retention was evident at 48 hours. Recovery of ioversol in urine and feces averaged 86% to 88% of the administered dose, of which all but a few percent was recovered in urine. On chromatographic assay, ioversol accounted for an average of 103% to 109% of radioiodine, suggesting, within the experimental limits of the assay, that ioversol is excreted unchanged. No dose-related differences were evident in any of these measures. The pharmacokinetics and biodistribution of ioversol are consistent with those of other extracellularly distributed iodinated contrast agents that are excreted by the kidney.

Relationship of ATP Turnover, Polyphosphoinositide Metabolism, and Protein Phosphorylation in Sciatic Nerve and Derived Peripheral Myelin Subfractions from Normal and Streptozotocin Diabetic Rats

Sciatic nerve from streptozotocin-induced diabetic rats has previously been shown to incorporate more 32P into phosphatidylinositol-4,5-bisphosphate (PIP2) and the principal myelin proteins than normal nerve. In the present study, labeling of ATP and PIP2 was compared. Using nerve segments, [gamma-32P]ATP specific activity reached a plateau after incubation for 4 h with [32P]orthophosphate, whereas the specific activity of [32P]PIP2 rose much more slowly and was still increasing after 8 h. The rate of disappearance of radioactivity from prelabeled ATP was biphasic, with 75% being lost within 30 min and the remainder declining much more slowly for several hours thereafter. In contrast, no decrease in prelabeled PIP2 radioactivity could be detected for up to 4 h. The kinetics of ATP metabolism were not appreciably different for normal and diabetic nerve. However, after incubation with [32P]orthophosphate for 2 h, the specific activity of PIP2 was 50-120% higher in diabetic nerve. This phenomenon, therefore, cannot be ascribed to altered specific activity of the ATP precursor pool. Greater labeling of PIP2 in 32P-labeled diabetic nerve was present in purified myelin isolated using a simple discontinuous sucrose density gradient, but not in a "nonmyelin" fraction. When nerve homogenate was fractionated on a more complex gradient, three myelin-enriched subfractions were obtained which were heterogeneous as judged by morphological appearance, protein profile, and lipid metabolic activity. The proportion of total lipid radioactivity accounted for by PIP2 was elevated in all the subfractions relative to the homogenate. As compared to myelin subfractions from normal nerve, an increased percentage of 32P in PIP2 was obtained only in the major myelin subfraction from diabetic nerve. The phosphorylation of P0 relative to the other myelin proteins was also enhanced in this subfraction in nerve from diabetic animals.

Influence of circulating epinephrine on absorption of subcutaneously injected insulin.

Effects of epinephrine (Epi) infusion on the absorption of subcutaneously injected 125I-labeled soluble human insulin (10 U) from the thigh or the abdomen were studied in 16 healthy subjects and from the thigh in 10 insulin-dependent diabetic (IDDM) patients. Epi was infused at 0.3 (high dose) or 0.1 (low dose; healthy subjects) nmol.kg-1.min-1 i.v., resulting in arterial plasma Epi levels of approximately 6 and 2 nM, respectively. Saline was infused on a control day. Insulin absorption was measured as disappearance of radioactivity from the injection site and as appearance of plasma immunoreactive insulin (IRI). Adipose tissue blood flow was measured with the 133Xe clearance technique. First-order disappearance rate constants of 125I from the thigh depot decreased approximately 40-50% during the high dose of Epi compared with control (P less than .001). The corresponding decrease from the abdominal depot was approximately 40% (P less than .001), whereas no significant change was found during the low Epi dose. IRI fell compared with control in all groups at the high Epi dose. The Epi-induced depression of insulin absorption occurred despite unaltered or even slightly increased subcutaneous blood flow. The results indicate that circulating Epi at levels seen during moderate physical stress depresses the absorption of soluble insulin from subcutaneous injection sites to an extent that might be important for glycemic control in IDDM patients. Furthermore, dissociation is found between changes in insulin absorption and subcutaneous blood flow during Epi infusion, suggesting that factors other than blood flow may also influence the absorption of subcutaneously injected insulin.

Distribution of Amino Acids to Internal Tissues After Epidermal Uptake in the Annelid Glycera Dibranchiata

ABSTRACT Net uptake rates by Glycera dibranchiata Ehlers of 18 amino acids, each present in artificial sea water at an initial concentration of 1 μmol 1-1, were estimated using high-performance liquid chromatography (HPLC). Uptake rates for 14C-labelled alanine, arginine, aspartate, glutamate, glycine and serine, presented singly at an initial concentration of l μmoll−1, were estimated by observing disappearance of radioactivity from the ambient solution. Net entry of alanine, arginine, aspartate and serine was estimated by HPLC in parallel samples of the medium. There was no significant difference in the rate of influx of labelled substrate and net entry estimated by HPLC for these amino acids. Ligature of the anterior and posterior ends of the worms did not perceptibly modify rates of uptake. Distribution of radioactivity to the internal and external body wall, coelomocytes, gut and coelomic fluid was observed after lh of incubation in lμmol11 serine. Rates of exchange of labelled carbon were estimated for all combinations of these internal tissues by taking advantage of morphological features of Glycera. Amino acid pools in each of the tissues of the worms are described, based on HPLC analyses. Internal distribution of radioactivity derived from [14C]serine is com-pared with total pools based on estimates of tissue volume and the normal serine content of free amino acid pools for each tissue. The distribution of the non-metabolized analogue cycloleucine is also described at the end of lh of incubation.

The active synthesis of phosphatidylcholine is required for very low density lipoprotein secretion from rat hepatocytes.

Hepatocytes obtained from rats fed a choline-deficient diet for 3 days were cultured in a medium +/- choline (100 microM) or methionine (200 microM). We investigated how choline deficiency affected hepatic lipogenesis, apolipoprotein synthesis, and lipoprotein secretion. The mass of triacylglycerol and phosphatidylcholine secreted was increased about 3-fold and 2-fold, respectively, by the addition of either choline or methionine to the cultured cells. Similarly, a 3-fold stimulation in the secretion of [3H]triacylglycerol and [3H]phosphatidylcholine derived from [3H]oleate was observed after the addition of choline or methionine. Fractionation of secreted lipoproteins by ultracentrifugation revealed that the reduced secretion of triacylglycerol and phosphatidylcholine from choline-deficient cells was mainly due to impaired secretion of very low density lipoproteins (VLDL) (but not high density lipoproteins (HDL)). Fluorography of L-[4,5-3H]leucine-labeled lipoproteins showed a remarkable inhibition of VLDL secretion by choline deficiency. The addition of choline or methionine stimulated the synthesis of phosphatidylcholine and increased the cellular phosphatidylcholine levels to that in normal cells. While there was little effect of choline on the synthesis and amount of cellular phosphatidylethanolamine, the addition of methionine diminished cellular phosphatidylethanolamine levels. Choline deficiency did not change the rate of incorporation of L-[4,5-3H]leucine into cellular VLDL apolipoproteins, nor the rate of disappearance of radioactivity from L-[4,5-3H]leucine-labeled cellular apoB, apoE, and apoC. These results suggest that hepatic secretion of VLDL, but not HDL, requires active phosphatidylcholine biosynthesis. Secondly, the inhibitory effect of choline deficiency on VLDL secretion can be compensated by the methylation of phosphatidylethanolamine.

Metabolic fate of anti-ulcer drug TEI-5103. (II). Distribution, foeto-placental transfer and excretion into milk in rats.

The distribution of 14C-TEI-5103 after single administration (oral: 200 mg/kg, intravenous: 10 mg/kg) and repeated oral administration (200 mg/kg/day) were studied in rats. The passage of radioactivity after oral administration of 14C-TEI-5103 (200 mg/kg) from mothers into the foetuses and the milk were studied in the pregnant and lactating rats, respectively. After single oral administration of 14C-TEI-5103, the radioactivity was high in the gastric wall and intestine, secondly in the liver and kidney of rats. The radioactivity in the other organs and tissues were lower than that in plasma. After intravenous administration, the radioactivty distributed mainly in the liver, intestine and kidney, but extremely low in the brain and spinal cord. After both administration, the disappearance of radioactivity in the organs and tissues was rapid. In case of repeated oral administration for 13 days, the radioactivity in the plasma, reached a plateau at least by the 4 th dosing and in the range of 0.9-1.2 times after single administration. The values of the tissue-to-plasma concentration ratio at 1 hr after repeated dose was almost same as that after a single dose. The accumulation in all tissues was very low. The passage of radioactivity from mothers into the foetuses and the milk in the pregnant and lactating rats, was extremely low.

Estimation of rRNA synthesis and degradation rates in senescing wheat leaves

Changes in cytoplasmic and chloroplast rRNA content and rates of rRNA synthesis and degradation of detached wheat leaves were determined. It was found that rRNA loss is proportionally higher in chloroplasts than in cytoplasm. Rates of synthesis were measured by incorporation of large amounts of [ 3H]orotic acid into rRNA. This approach overcame size differences between pyrimidine pools of cells under different physiological status. Furthermore, these pools reached nearly the same specific radioactivity as that of the administered solution. Rates of degradation were estimated either as the difference between synthesis and net variation of rRNA or by disappearance of radioactivity from 32P-labeled rRNA. Results indicated a decrease in the net rRNA synthesis capacity of leaves after 48 h of detachment. However, the fractional rates of rRNA synthesis were maintained in both cytoplasm and chloroplasts. Ribosomal RNA degradation rates were 2.5-fold higher in chloroplast than in cytoplasm. The observed chloroplast rRNA loss is due to an increased degradation rate which is 15-fold higher than the synthesis rate 48 h after detachment.

The effect of dietary cellulose on life span and biochemical variables of male mice

Sixteen month old C57BL/6J male mice were fed either a nutritionally adequate diet or this diet diluted with either 33% or 50% cellulose. The life span of the animals fed the latter two diets was longer than that of the controls, but only statistically significant in the animals fed the diet diluted with 50% cellulose. The rates of cellular protein synthesis were estimated in liver by determining: 1) the half lives of proteins by the rate of disappearance of radioactivity following the intraperitoneal injection of C14 labeled sodium bicarbonate, and 2) the cellular protein levels estimated by the concentration of proteins and DNA of the tissue. The rates of disappearance of radioactivity from the liver proteins of mice were not statistically significantly affected by these dietary regimens. However, there was a 27% decrease in the cellular protein synthesis of liver in the animals fed the diets containing cellulose.

Nitrogen Utilization in Lemna

(13)N-labeled nitrate was used to trace short-term nitrate influx into Lemna gibba L. G3 in experiments where disappearance of both radioactivity and total nitrate from the incubation medium was measured continuously and simultaneously. In plants performing net nitrate uptake from an initial nitrate concentration of 40 to 60 micromolar, there was no discrepancy between net uptake and influx, irrespective of the N status of the plants, indicating that concomitant nitrate efflux was low or nil. Plants treated with tungstate to inactivate nitrate reductase were able to take up nitrate following induction of the uptake system by exposure to a low amount of nitrate. Also, in this case, net uptake was equivalent to influx. In tungstate-treated plants preloaded with nitrate, both net uptake and influx were nil. In contrast to these observations, a clear discrepancy between net uptake and influx was observed when the plants were incubated at an initial nitrate concentration of approximately 5 micromolar, where net uptake is low and eventually ceases. It is concluded that plasmalemma nitrate transport is essentially unidirectional in plants performing net uptake at a concentration of 40 to 60 micromolar, and that transport is nil when internal nitrate sinks (vacuole, metabolism) are eliminated. The efflux component becomes increasingly important when the external concentration approaches the threshold value for net nitrate uptake (the nitrate compensation point) where considerable exchange between internal and external nitrate occurs.

Isotopic test of capillary permeability to albumin in diabetic patients: Effects of hypertension, microangiopathy, and duration of diabetes

Capillary permeability to albumin (CPA) was studied by performing an isotopic noninvasive test with venous compression on 87 nonselected diabetics with no edema, no cardiac failure, and no peripheral vascular disease. Excessive albumin retention (AR ≥ 8%) ten minutes after removal of the compression was found in 27 patients (31%). The radioactivity disappearance curve was then analyzed using the Fast Fourier Transform (FFT). An abnormal isotopic CPA test was thus found in at least 45 out of the 87 patients. The prevalence of an abnormal test was not different in type 1 and type 2 diabetics. We studied the independent effects of hypertension, presence of specific clinical signs of microangiopathy (retinopathy and/or significant proteinuria), and duration of diabetes. Among diabetics free of specific clinical signs of microangiopathy, the prevalence of an AR ≥8% was significantly higher in those with hypertension ( 11 19 ) than in those with normal blood pressure ( 2 28 ) and in nondiabetic hypertensive patients ( 0 16 ). Among normotensive diabetics, the prevalence of an abnormal test was higher, but not significantly, in patients with specific clinical signs of microangiopathy ( 8 11 ) than in those free of them ( 7 18 ). Seven normotensive diabetics without specific clinical signs of microangiopathy had an abnormal test; five of them had had diabetes for more than five years. The prevalence of diabetes of more than five years duration was significantly higher in patients with an abnormal test ( 35 45 ) than in normotensive diabetics free of specific clinical signs of microangiopathy with a normal test ( 4 11 ). These results show (1) the high prevalence of an abnormal CPA in a nonselected diabetic population, (2) the major independent roles of hypertension, microangiopathy, and duration of diabetes in this abnormality, and (3) with the FFT, evidence of a late abnormal phenomenon in the radioactivity disappearance curve, which may be due to a deficient lymphatic wash-out of albumin preceding overt albumin retention.

Disposition of moracizine (ethmozine) in healthy subjects after oral administration of radiolabelled drug.

Moracizine (ethmozine) is a phenothiazine derivative with demonstrated antiarrhythmic activity. To characterize the pharmacokinetics and material balance relationships in humans, we have given 14C-moracizine X HCl as a single oral dose of 500 mg (50 microCi) to six healthy men. Plasma, urine, and faecal samples were collected for 7 days after administration and the concentrations of total radioactivity and intact moracizine were determined by liquid scintillation counting and HPLC, respectively. Urine and faecal recovery accounted for 95% of the administered radioactivity. Most of this radioactivity was found in the faeces (59%). Only 0.05% of the dose was recovered from urine as intact moracizine. The Cmax and AUC for moracizine equivalents of total radioactivity were 4- and 18-fold higher, respectively, than the corresponding values for intact moracizine. Additionally, both the disappearance of total radioactivity from plasma and its excretion rate into urine were slower in comparison to intact drug. Terminal t1/2 values calculated from plasma concentration-time data were 85.2 and 3.5 h for total radioactivity and intact moracizine, respectively. However, based on urinary excretion rates, the t1/2 for total radioactivity was shorter (29.3 h) while the t1/2 for intact drug was comparable (2.7 h) to the results obtained from the plasma data. The oral plasma clearance of moracizine was relatively large (2.2 l X min-1), suggesting first-pass metabolism. The estimated oral systemic availability of moracizine was 34%.

A quantitative cerebral and whole body autoradiographic study of a intravenously administered benzodiazepine antagonist 3H-Ro 15-1788 in mice.

3H-Ro 15-1788, a benzodiazepine receptor antagonist, was injected IV into male and pregnant mice. Autoradiograms were prepared from sagittal sections of animals killed after 30 s to 48 h. In the adult animal there was a rapid and high initial accumulation of radioactivity in the brain as compared to other organs and tissues. The highest accumulation was found in cortical brain areas, such as the olfactory bulb and the frontal cortex. Cerebellar cortex, globus pallidus, amygdala, substantia nigra, colliculus, hippocampus and pons followed in rank order. The rate of decline of radioactivity was highest in the pons and lowest in the olfactory bulb. The initial disappearance of radioactivity from the cerebellum was higher than from the other brain regions. Ro 15-1788 was rapidly eliminated; 4 h after drug administration there was an almost complete clearance of radioactivity from all tissues. After 24 h no trace of activity remained in the animal. The distribution of radioactivity at later time points indicates that metabolites of Ro 15-1788 are eliminated by fecal, urinary and nasal secretion. In the fetus also there was an early accumulation of radioactivity in the central nervous system. The radioactivity in fetal organs was lower than in the mother at all time intervals.

The effect of circulating growth hormone-binding protein on metabolic clearance, distribution, and degradation of human growth hormone.

We recently described a specific binding protein for human GH (hGH) in human plasma, with which a substantial portion of circulating hGH is complexed. The biological function of the complexed fraction is unknown. To test the hypothesis that complexed hGH may have different in vivo kinetics than free hGH, we compared the MCRs, distribution volumes (Vd), and degradation rates of complexed and free [125I] hGH in the rat. A partially purified GH-binding protein preparation, generated by affinity chromatography on a hGH column, was used for this purpose. A mixture of hGH with binding protein (equivalent to the amount contained in 0.9 mL human plasma) was injected iv as a single dose. Parallel experiments were conducted with hGH in the absence of binding protein. Disappearance of total, immunoprecipitable, and trichloroacetic acid-precipitable radioactivity from rat plasma was followed, and MCR, Vd, and degradation rates were derived by standard mathematical techniques. The MCR was 6-fold slower for complexed than for free hGH (2.3 vs. 14 mL/min X kg), Vd was 4-fold smaller for complexed hGH than for free hGH (71 vs. 256 mL/kg), and initial degradation rate was 4.5-fold lower for complexed than for free hGH (13.2% vs. 59.9%/15 min). The Vd of complexed hGH was close to the intravascular volume, while the Vd for free hGH corresponded to the extracellular volume. We conclude that one function of the hGH-binding protein is relative confinement of hGH to the vascular compartment, thereby protecting it from degradation and prolonging its biological half-life.