Lia Savu

Serum depletion of corticosteroid binding activities, an early marker of human septic shock

Abstract We report that human sera within 24 hours after the onset of septic shock are virtually depleted of the corticosteroid binding activities characteristic for transcortin. By contrast, transcortin activities are not changed significantly in cases of acute inflammation, though septic shock and inflammatory sera are comparable in other respects: they show similar responses of their haptoglobin, thyroxine binding prealbumin, endogenous cortisol and progesterone levels. The physiological meaning and clinical interest of these results are discussed.

Corticosterone binding globulin: an acute phase “negative” protein in the rat

We report a novel effect of an induced inflammatory process on the serum proteins of the rat: the acute phase of the inflammation is accompanied by a dramatic decrease of corticosterone-binding globulin (CBG or transcortin) activities in the normal and the 19-day pregnant adults; at the same time, the exceptionally high fetal CBG activities of this pregnancy stage [l] are not affected. Analysis of binding parameters reveals that the observed variations are due to a fall in the number of binding sites, whereas the affinity of the protein for the hormone is not significantly modified. This is, to our knowledge, the first report on the implication of a specific high affinity serum hormone carrier in an inflammatory reaction.

A senescence up-regulated protein: the rat thyroxine-binding globulin (TBG)

Thyroxine-binding globulin (TBG), the major carrier of thyroid hormones in human serum, was thought to be absent in most species, including rodents. We demonstrated recently that in fact the rat possesses a TBG gene, virtually non-expressed in young adults, but actively transcribed during post-natal development. We now find that the TBG gene is also increasingly re-expressed during senescence. Evidence is presented suggesting that physiologically decreased thyroid hormone levels, characteristic of neonates and of ageing rats, might constitute a common factor inducing up-regulation of TBG in both developmental and ageing processes. Rat TBG is to our knowledge the first biochemical positive (i.e. increasing) marker of non-pathological senescence, expressed at both biosynthetic and bloodstream levels.

A thyroxine binding globulin (TBG)-like protein in the sera of developing and adult rats

We report evidence based on equilibrium binding, electrophoretic, autoradiographic studies, that the rat possesses a major high affinity thyroid hormone binding protein, with an electrophoretic mobility and binding properties similar to those of the human thyroxine binding globulin (TBG). We show that in the sera of postnatal developing animals, the thyroxine and the triiodothyronine binding activities increase up to 10 times over adult or foetal levels, due to a high transient post-natal surge of the rat TBG. In the adult serum, the TBG persists in decreased amounts: it then yields the predominant role as thyroxine carrier to the thyroid binding prealbumin, but retains the major role as binder of triiodothyronine i.e. of the biologically active thyroid hormone.

The hepatic biosynthesis of rat thyroxine binding globulin (TBG): Demonstration, ontogenesis, and UP-regulation in experimental hypothyroidism

Using a human thyroxine binding globulin (TBG) cDNA probe, we demonstrate that rat liver contains two TBG mRNA species of different length, consisting of about 1.8 Kb and 2.4 Kb respectively. Slot blot analysis of the hepatic mRNAs from rats of different age reveals a fair correlation between the developmental trend of the messengers and that of the TBG circulating levels. Finally Northern blot and slot studies demonstrate that the increase of serum TBG induced in adults by thyroidectomy actually reflects an enhanced hepatic biosynthesis of the protein.

Total and unbound cortisol-, progesterone-, oestrone- and transcortin-binding activities in sera from patients with myocardial infarction: evidence for differential responses of good and bad prognostic cases.

Abstract. Day‐of‐admission sera from myocardial infarction patients (MI) and patients with cardiopathies other than MI (non‐MI) were analysed for total and unbound Cortisol (F), progesterone (P4), oestrone (E1), and corticosteroid binding activities (CBG).

Thyroxine-binding globulin and thyroxine-binding prealbumin in hypothyroid and hyperthyroid developing rats

We present evidence based on equilibrium and non-equilibrium binding studies, as well as on immunological techniques, that of the two rat specific thyroid-hormone-binding proteins, i.e., thyroxine-binding globulin (TBG) and thyroxine-binding prealbumin (TBPA), TBG but not TBPA is regulated by the thyroid hormones (TH). Hypothyroidism, induced from the day of birth by daily treatment with propylthiouracil (PTU-rats), leads to dramatic and sustained increases of the TH-binding abilities of the sera measured at equilibrium, whereas hyperthyroidism, induced by treatment with thyroxine (T4-rats), leads to the decrease of these abilities. Polyacrylamide gel electrophoresis and isoelectrofocalisation of radioiodinated T4-labelled sera, together with immunoassay of TBPA, demonstrate that both effects are due to TBG, the levels of which rise in PTU-rats and decline in T4-rats, while TBPA levels do not respond to either depletion or excess of the thyroid hormones. TBG rather than TBPA appears as the key thyroid-hormone-binding protein of the rat, inasmuch as it alone expresses a regulatory function of the thyroid hormones at protein synthesis level.

Relations between fatty acids and oestrogen binding properties of pure rat alpha1-foetoprotein

A delipidation procedure based on treatment with charcoal at pH 3 has been applied to highly purified rat alpha 1-foetoprotein preparations. The oestrogen binding properties of the delipidated proteins have been studied with an equilibrium dialysis technique, and compared with the properties of the untreated foetal protein, as well as those of preparations reconstituted from the defatted alpha 1-foetoprotein and the removed lipids. An important increase has been evidenced for the binding levels of oestrone, oestradiol-17 beta and diethylstilboestrol by the delipidated alpha 1-foetoprotein. A reversal of this effect has been obtained by incubating the delipidated protein either with the lipids extracted from the purified alpha 1-foetoprotein or with a potent competitor of the rat alpha 1-foetoprotein-oestrogen interaction, designated as L, previously demonstrated and isolated from whole rat sera, and tentatively characterized as a mixture of fatty acids. Scatchard analysis of the oestrone and oestradiol-17 beta binding parameters show that the enhanced fixation of the hormones after defatting is primarily due to a two-fold increase of the apparent number of binding sites/mol alpha 1-foetoprotein. The results are interpreted in terms of the probable, at least partial, identity between the lipids closely associated with the pure alpha 1-foetoprotein and the fatty acid mixture L isolated from whole sera. The possible biological role of complex interplay between oestrophilic alpha 1-foetoproteins, phenolsteroids and fatty acids in the control of oestrogen levels during development is discussed briefly.

OESTROGEN BINDING FUNCTION OF ALPHA1-FETOPROTEIN

Abstract The discovery of a protein with high specific affinity for oestrone and oestradiol in the sera of rat and mouse at a period of intensive cellular development and sexual maturation has directed our researches primarily towards the possible role of this protein in the functions of the oestrogen hormones. One of our approaches has been a detailed study of the hormonal milieu during the perinatal growth in the rat. We have thus been able to demonstrate, along with “true” oestrogens, the presence of alternative serum ligands for alpha 1 -fetoprotein, either reactive or unreactive towards specific antioestrogen antibodies. We shall mainly concern ourselves with the preliminary characterization of the latter class of alpha 1 -fetoprotein ligands and show their ability to compete for oestrogen binding sites on oestrophilic alpha 1 -fetoproteins. Their possible role in the mechanism of action of oestrogens will be discussed.

Binding activities of thyroxine binding globulin versus thyroxine binding prealbumin in rat sera: Differential modulation by thyroid hormone ligands, oleic acid and pharmacological drugs

We use gel equilibration and electrophoretic techniques to compare the binding properties of thyroxine binding globulin and thyroxine binding prealbumin in rat sera. The evidence indicates that TBG bears the serum lowest capacity highest affinity sites for thyroxine (T4) and triiodothyronine (T3) (Ka1 greater than or equal to 10(9) M-1) as well as weaker saturable T3 sites (Ka2 approximately 10(8) M-1). TBPA bears for T4 only Ka2 approximately 10(8) M-1 sites and for T3 only Ka approximately 10(6) M-1 sites. Consistent with these parameters are the specific responses of TBG and TBPA binding activities to varying serum concentrations of T4, T3, oleic acid, the drugs diphenylhydantoin or salicylate. The primary attack of these compounds is aimed at TBG. Small T4, oleate or DPH doses chase the TBG-bound T4 to TBPA, high doses of T4 or oleate but not of DPH inhibiting the T4 binding to both proteins. In the T3-serum interactions, all tested compounds displace the TBG-bound hormone without chasing it to TBPA. The high reactivity of TBG sites designates the protein as crucially involved in modulating the free vs bound serum levels of T4 and T3 against physiological or pathological variations of binding competitors.