Catabolic sites of human interferon-gamma

Recombinant human interferon-gamma (HuIFN-gamma) injected into rabbits disappeared from the circulation more rapidly than natural IFN-gamma. The latter displayed an initial decay curve more rapid than that for natural HuIFN-alpha although 4 h after injection plasma levels were similar. This result suggests that IFN-gamma has pharmacokinetic properties different to those of IFN-alpha which may be explained by considerable and simultaneous hepatic and renal catabolism. Surprisingly, the hepatic uptake of recombinant (unglycosylated) IFN-gamma was more marked than uptake of natural IFN-gamma. Moreover, both IFN-gamma preparations were cleared by the isolated and perfused kidney and once again the recombinant IFN disappeared more rapidly. This result does not conform with the suggestion that IFN-gamma exists as a tetramer which would not be filtered by the glomerulus, but is consistent with the pharmacokinetic behaviour shown in vivo.

Microfilament organization in human platelets

Morphological and biochemical studies suggest that actin in human platelets polymerizes from monomers or oligomers into long filaments more tightly structured in activated than in resting platelets. The polymerization and reorganization of actin filaments are regulated by cellular proteins. Profilin prevents actin polymerization by forming tight complexes with monomeric actin; gelsolin acts both severing filaments and inhibiting their elongation by capping at the barbed end; other actin-binding proteins nucleate polymerization and cross-link actin filaments into networks or bundles. The changes in the actin assembly state, which are under the control of calcium, seem essential for pseudopodal formation. Other platelet processes, such as granule centralization and contractile gel formation, are due to calcium-dependent actin-myosin interaction. In addition, Ca++ seems to inhibit through calmodulin the binding of caldesmon to actin, allowing actin linkage to myosin in a 'flip-flop' fashion.

Pharmacokinetics of human lymphoblastoid interferon in rabbits

By intravenous (bolus) administration of large amounts (29 Mega Units) of lymphoblastoid interferon into rabbits, it has been possible to detect circulating antiviral activity (0.02% of the dose) up to 18 hr post-injection and to determine for the first time the pharmacokinetic parameters. The slow component (elimination phase) has a half-life of 235 +/- 9 min. The total apparent volume of distribution is 2,564 +/- 1,497 ml which is far larger than the combined plasma-extracellular volumes. This suggests a IFN dilution due to its extensive binding to cell receptors. The clearance of 7.3 +/- 4.1 ml/min is an index of the rate of renal and cellular (internalization of the receptor-ligand complex) catabolism of IFN. Pharmacokinetic parameters are useful for devising an administration schedule of IFN as an antiproliferative agent but are not predictive of an immunological response if IFN is used as an immuno-adjuvant.

Pulmonary catabolism of interferons: alveolar absorption of 125I-labeled human interferon alpha is accompanied by partial loss of biological activity

The catabolism of interferon was examined in isolated rabbit lungs which were ventilated and perfused with homologous blood. Natural human interferon-alpha (HuIFN-alpha) from lymphoblastoid Namalwa cells or recombinant DNA-derived HuIFN-alpha 2 were labeled with 125I, mixed with an excess of the respective cold interferons and added to the perfusion blood. Protein-bound and acid-soluble radioactivity, as well as antiviral activity, were measured at regular time intervals. During the first 3 h of perfusion, only very small fractions of the interferons disappeared from the perfusate, irrespective of whether lungs were inserted in the perfusion system. This indicated that catabolism of interferons in the pulmonary circulation was negligible. On the other hand, when the interferons were instilled into the bronchial-alveolar tree, absorption of antiviral activity differed from that of acid-precipitable protein-associated radioactivity. While most of the radioactivity was transferred into the perfusate, only 2% of antiviral activity of natural HuIFN-alpha and 30% of that of HuIFN-alpha 2 were recovered in the perfusate. In both cases acid-soluble radioactivity in the system reached about 10%. Since radioiodide, instilled in the bronchial-alveolar tree, was transported rapidly into the perfusate, this type of analysis did not help in locating the site(s) of degradation. Alveolar macrophages did not catabolize or inactivate interferons in vitro.

Degradation of human 125I-interferon alpha by isolated perfused rabbit kidney and liver

Rabbit livers and kidneys were isolated and perfused with homologous blood. After equilibration, human IFN alpha labeled with 125I and an excess of cold IFN alpha were added, and blood samples were withdrawn at predetermined times. Protein-bound and acid-soluble radioactivity together with biological (antiviral) activity were measured. Our results show that although liver exerts a minimal catabolism, the kidney filters and breaks down a considerable amount of IFN alpha. The parallelism between protein-bound radioactivity and biological activity decay curves indicates that IFN carefully labeled with 125I can be reliably used for metabolic investigations.

Renal metabolism of homologous serum interferon

The metabolic behaviour of homologous native and desialylated serum and urinary interferons has been investigated by using an isolated and perfused rabbit kidney, the performance of which is comparable to that in vivo. Serum native and urinary interferons disappear from the plasma perfusate with a fractional turnover rate of 1.8 and 2% and half-lives of 3 and 35 min, respectively. Serum desialylated interferon disappears much more rapidly in keeping with the finding that the glomerular sieve poses less steric hindrance and electrophysical repulsion to the passage of less anionic proteins. These results confirm and extend our previous findings, which indicated that the kidneys have a predominant catabolic role and can explain to some extent the rapid disappearance of interferon from plasma.

The role of liver in the catabolism of human alpha- and beta-interferon

The susceptibility of human leukocyte (alpha), fibroblast (beta) and recombinant alpha-2-interferons to clearance by the isolated and perfused rabbit liver has been evaluated. Human leukocyte and recombinant alpha-2-interferons were stable and their initial levels were maintained in the perfusate even if they had been treated with neuraminidase, thus suggesting that alpha-interferons have no exposed sugars recognizable by hepatic binding proteins. On the other hand, native, and particularly desialylated human beta-interferon, underwent marked hepatic uptake confirming the importance of the liver as a catabolic site for glycosylated interferons.

The kidney is the main site of interferon catabolism

The fate of human natural interferons alpha and beta and of recombinant (R) alpha 2 has been investigated by using an isolated and perfused rabbit kidney preparation with a normal physiological performance. A remarkable amount of IFN is filtrated in a monoexponential fashion, reabsorbed and very likely degraded in tubular cells with negligible excretion in the urine. The disappearance rate of HuRIFN-alpha 2 is higher than natural HuIFNs-alpha and beta and is in keeping with the lower molecular weight of RIFN-alpha 2. Differences in molecular charge or shape are probably responsible for the slightly reduced filtration of IFN-beta. Pharmacokinetic studies in animal models appear instructive and useful for devising improved dosage schedules in clinical trials.

Renal metabolism of rabbit serum infection

Three different approaches have been used to evaluate the catabolism of rabbit serum interferon (IFN) by the kidneys. Firstly, in normal rabbits the disappearance of exogenous IFN from plasma was very rapid, whereas it was significantly slower after bilateral nephrectomy. Secondly, the IFN level in arterial blood was always higher than in renal venous blood: the mean renal extraction rate of IFN in the rabbit, with a renal plasma flow of 9 ml/min, was about 1 ml/min. Thirdly, a selective and reversible tubular damage induced by maleate before intravenous administration of IFN significantly inhibited luminal uptake of IFN and markedly increases the interferonuria. All of these results support the view that the kidneys have a preponderant role in IFN filtration, catabolism and excretion.

Renal filtration, absorption and catabolism of human alpha interferon

The renal handling of human interferon-alpha has been evaluated by using an isolated and perfused rabbit kidney. IFN-alpha disappears from plasma with a t1/2 of 81 min and the fractional turnover rate is 0.84%/min. About 47 molecules of IFN-alpha are filtrated with 100 molecules of creatinine but most of the IFN is absorbed by tubular cells. This is the first report showing that human IFN-alpha is filtrated by the kidney, largely absorbed, most probably catabolized within tubular epithelium and excreted in negligible amounts with the urine.

Excellent performance of the isolated rabbit kidney perfused with platelet and leukocyte-poor blood

It has been shown that the isolated rabbit kidney, perfused with fresh homologous, platelet- and leukocyte-poor blood, has a functional performance almost equivalent to the kidney in vivo. This is the first report that strongly indicates the deleterious role of platelets and leukocytes in blood when used as a perfusing medium.

Poor performance of the isolated rabbit kidney perfused with free-cell media and whole blood

All of these results indicate that the isolated rabbit kidney, perfused either with free-cell media or with whole blood, shows marked functional deficiencies and cannot be considered a reliable preparation. The former media do not induce vasoconstriction but are unable to insure a correct cations reabsorption, while the latter causes intense renal vasospasm and clogging of the glomerular circulation indicated by high arterial pressure and hematuria. On the basis of these observations it appears indispensable to use a perfusion medium capable of eliciting renal autoregulation but deprived of blood elements such as platelets and leukocytes that may be either directly or indirectly responsible for the glomerular clogging. This problem is considered in the following communication.

[Proposal for the introduction of a new substance into hospital practice: dipropyl acetate sodium in the prevention and treatment of alcoholic delirium]

Reference is made to two years' work with the sodium salt of N-dipropylacetic acid in the prevention and treatment of alcoholic delirium tremens in 1500 subjects. The drug impeded the onset of the syndrome, or reduced its duration and gravity in cases where it was already present. It appeared suitable for the specific correction of the CNS functional changes responsible for delirium tremens.

Metabolism of interferon: hepatic clearance of native and desialylated interferon

The effect of removal of sialic acid on the survival of rabbit serum and urinary interferon (IF) has been investigated in isolate, perfused rabbit liver preparations. In contrast with native IF, which may be already partially desialylated. IF freed of 80 to 90% of its sialic acid was rapidly cleared from the perfusate of normal livers, or livers pre-treated with actinomycin D. The results suggest that the mechanism of IF catabolism by the liver is similar to that reported for several other circulating glycoproteins.

The role of sialic acid in determining the survival of circulating interferon

Rabbit interferon has been extensively desialytated and its metabolic behaviour has been evaluated in the rabbit. The half-life of asialointerferon is significantly shorter than the native interferon and its urinary excretion becomes negligible. Moreover the rapid uptake of asialointerferon by the isolated and perfused rabbit liver, suggests a hitherto unsuspected catobolic pathway for this glycoprotein.

Werdnig-Hoffmann-Wohlfart-Kugelberg-Welander disease. Nosological unity and clinical variability in intrafamilial cases

Two members of an Italian family are affected with progressive spinal muscular atrophy. One, a male, has had the disease since his early infancy and, though severely disabled, is still living at the age of 13. In his sister, the first symptoms appeared at the age of 15, and the disease seems to be rapidly advancing. Their parents were consanguineous. Their mother, however, married twice, her second marriage being nonconsan-guineous and producing no affected children.

The study of this family and an analysis of the literature led to the following conclusions: (a) early onset of the disease does not necessarily mean that the course will be malignant; (b) the disease usually has a similar onset and course in subjects belonging to the same family.

In many families, however (and these have been examined in the present paper) malignant Werdnig-Hoffmann disease is found to coexist with the Werdnig-Hoffmann disease with a prolonged course, the Wohlfart-Kugelberg-Welander disease with infantile onset, and the Wohlfart-Kugelberg-Welander disease with juvenile onset. We feel, therefore, that from a genetic point of view all these forms should be included into one and the same group.