Effect of neonatal treatment with monoclonal antibody to thyrotropin (TSH) receptor on the thyroxin (T4) level and certain parameters of the internal genital organs of adult rats.

Treatment of newborn rats with a single dose of monoclonal antibody to TSH receptor, caused permanent changes in the body weight, T4 level, and different sexual parameters. There are considerable sex and organ dependent differences in the sensitivity. Body weight and physical condition of males deteriorates, while the condition of the females is constant. However, T4 level of females significantly increases while that of the males does not change. The weight of seminal vesicle increases, while ovarian weight decreases. Effect of hCG treatment in adult age is inhibited by neonatal antibody (to TSH receptor) treatment. The experiment calls the attention to the imprinter effect of antibodies in the neonatal critical period, which effect could be manifested on the antibody's own (provoked) or foreign (related) receptor.

Changes in binding of monoclonal antibodies to TSH receptor following thyrotropin (TSH) and gonadotropin (GTH) pretreatments (studies on human thyroid and CHO cell lines).

Monoclonal antibody to TSH-receptor binds to the cells of human thyroid gland and to Chinese hamster ovary cell cultures. Pretreatments with TSH can decrease the binding of antibody, which effect is more expressed in CHO than in thyroid cells. Gonadotropin (FSH + LH) cannot influence the binding of antibody to thyroid, but there is an effect on CHO cells. Endotoxin (lipopolysaccharide, LPS) can depress the binding of antibodies on both objects and abolishes the difference between thyrotropin and gonadotropin receptors in their binding capacity, on both cell types. The experiments prove the similarity of thyrotropin and gonadotropin receptors which is responsible for the hormonal overlap.

Influence of experimentally induced endotoxemias on the thyroid function of rats.

The general membrane-damaging effect of endotoxins (LPS) may be also demonstrated on the follicular cells of thyroid gland. Serum T4 level significantly decreased and the response of thyroid gland to exogenous THS was markedly inhibited in experimental endotoxin and other so-called enteroendotoxemic shocks (e.g. intestinal ischemia, tourniquet shock, intestinal syndrome of radiation disease). A single subtoxic dose of LPS given to newborn rats decreased the T4 level, the response of thyroid to TSH in adulthood and caused a somatic retardation. The radio-detoxified endotoxin (TOLERIN) did not inhibit the thyroid response to TSH. TOLERIN pretreatment protected the rats against LPS and other enteroendotoxemic shocks.

Effect of gonadotropin (FSH-LH) and thyrotropin (TSH) treatment in adolescence on TSH-sensitivity in adult rats.

Hormonal imprinting is characteristic of the neonatal age, in which the receptor of the target cell matures, i.e. acquires its adult binding capacity, and cellular response becomes established in presence of the adequate hormone. The normal course of imprinting may be altered by certain molecules (related hormones, hormone analogons) which are able to bind to the receptor of the adequate hormone. The chemically related gonadotropic and thyrotropic hormones may overlap on each other's receptors not only in the perinatal age, but also in the early adulthood, and this overlap of the binding may give rise to an imprinting-like effect. An example of this phenomenon was observed in the present study, in which rats of seven weeks of age treated with gonadotropin showed a significant decrease in thyroidic response to TSH, and exposure to TSH failed to increase their basic thyroxine concentration to the normal (control) level. This depressive effect of gonadotropin was slightly reduced in the presence of LPS (endotoxin), causing membrane perturbation, while pretreatment with LPS and TSH accounted for an increased sensitivity to TSH in later phases of the rat's life. These experimental observations support the possibility of a special form of imprinting in adolescence.

Effect of gonadotropin (FSH + LH) and thyrotropin (TSH) administered with or without endotoxin at the age of three weeks on the response capacity of the thyroid gland in adult rats.

At the age of three weeks the experimental animals received either thyrotropin (TSH), or gonadotropin (FSH + LH), or endotoxin (LPS) alone or in combination. The effectivity of the treatments was evaluated at the age of two months (with or without further hormone treatment). Contrastingly to neonatal TSH treatment, TSH treatment at the age of three weeks did not give rise to imprinting. In female animals, however, TSH treatment increased the sensitivity to the related gonadotropin hormone. At the age of three weeks gonadotropin treatment--on its own--did not cause damages to the TSH receptors of the thyroid gland. While in previous experiments neonatal endotoxin treatment damaged considerably the thyroxin production of the adult thyroid gland, after treatments at the age of three weeks no similar effect could be observed. The treatment, however, decreased the sensitivity of the receptors to TSH. In female animals simultaneous administration of endotoxin and TSH led, even without further hormone treatment, to constant increase in T4 level (the increase could also be detected in the adult animal). Imprinting, however, did not develop. In male animals simultaneous administration of endotoxin and gonadotroph hormone decreased considerably the T4 baseline level, and further TSH or gonadotropin treatment was unable to enhance T4 production.

Effect of experimental shock conditions on the serum T4 level of rats and response of their thyroid gland to exogenous TSH.

150 min ligature of the superior (cranial) mesenteric artery (intestinal ischemia) significantly decreases serum T4 level and completely inhibits the response of the thyroid gland to exogenous TSH in rats. 300 min ligature of the hind limbs (tourniquet shock) decreases serum T4 level and the T4 response of thyroid gland to exogenous TSH in rats. The probable reasons for altered function of the thyroid gland in enteroendotoxemic shock conditions are discussed.

Effect of single neonatal melatonin treatment on in vitro thyroxin secretion and TSH or melatonin-modified cAMP level of one-month-old rats.

At the age of one month, incubation with melatonin of the thyroid glands of rats having received a single melatonin treatment at the age of three days resulted in increased thyroxine production. TSH was unable to enhance the thyroxine production of animals treated with melatonin neonatally, while its considerable increase could be observed in the case of control animals. Simultaneous TSH and melatonin treatment applied in vitro at the age of one month resulted in an approximately twofold increase of thyroid T4 production in rats having received neonatal melatonin treatment. In vitro alteration of the cyclic AMP level of the thyroid glands of intact and neonatally melatonin treated rats ran practically parallel, except that in the melatonin treated animals the cAMP level was higher after TSH administration. At the same time the cAMP level decreased in the thyroid gland of animals treated with TSH + melatonin. There was no exact correlation between the alterations of cAMP and T4 levels in the given experimental system.

Influence of hormonal imprinting on hormone level. Permanent receptor damaging effect of pituitary hormones administered to newly-hatched cockerels.

The overlapping effect of TSH and FSH on the gonad and on the thyroid gland can be demonstrated in cockerels even at the age of five weeks. These hormones influence the secretion of testosterone in a similar way and to a similar extent, while on the thyroxine level the influence of the specific hormone is more pronounced. Neonatal FSH and TSH treatment considerably decreased the basal testosterone level measured at the age of five weeks. Neonatal FSH treatment increased the basal T4 level while TSH treatment decreased it. The effect of TSH treatment administered at the age of five weeks in increasing the testosterone level was weakened after neonatal pretreatment with any iodine hormone. The effect of TSH treatment could only be inhibited by neonatal FSH pretreatment. Neonatal pretreatment with any of the trophormones caused a diminution of the T4 level augmenting of FSH and TSH administered at the age of five weeks.

Presence (hPL, prostaglandin) and absence (triiodothyronine, thyroxine) of hormones in Tetrahymena: experimental facts and open questions.

The RIA technique detected prostaglandin (PGF2) and human placetal lactogen (hPL) in Tetrahymena cultures grown in bacto tryptone + yeast extract medium which, however, itself contained these hormones. About one to two per cent of the total hormone content of the medium was demonstrated intracellularly. Treatment with diiodotyrosine (T2), which is known to stimulate the growth of Tetrahymena, was followed by a decrease in the intracellular prostaglandin level. Triiodothyronine and thyroxine were not detected in Tetrahymena or in the medium, and did not appear in it on induction with TSH either. In the light of these observations it might well be doubted that prostaglandin was native in Tetrahymena: the use of synthetic media, and/or a reliable demonstration of the hormone content of the growth medium is recommended for evidence of hormone biosynthesis by unicellular organisms.

Can neonatal treatment with a related hormone adapt the receptor for itself?

Treatment of rats with endotoxin immediately after birth caused destruction of the cell membrane, resulting in depression of the thyroxin level and of the response to thyrotropin in adulthood. The thyroid gland of the rats treated neonatally with endotoxin failed to differentiate TSH from gonadotropin. Neonatal treatment (imprinting) with thyrotropin or gonadotropin after preexposure to the endotoxin improved the adult response to the exogenous hormone presented for imprinting after endotoxin. It appears that during the reconstruction stage following upon membrane perturbation in the critical period of receptor maturation, the adequate hormone or a related molecule can equally adapt the receptor for itself, but neither can fully compensate the perinatal membrane injury, nor the consequent diminution of receptor activity.

Influence of the neonatal (clomiphene) inhibition of estradiol imprinting on gonadal development and gonadal and thyroid hormone production later in life.

Treatment of newborn rats with clomiphene citrate during the first 5 days of life gave rise to a marked decrease in body mass and to a still greater decrease in gonadal mass. A decrease was also observed in the testicular diameter of the males. The females showed a 43% increase in their estradiol levels over the control and an increase in the sensitivity to gonadotropins. Thyroxine level, which was also determined in view of the known gonadotropin-thyrotropin overlap, showed no change 6 weeks after pretreatment with clomiphene, while the thyroid gland responded to gonadotropin in the same manner as to thyrotropin.

Influence of a single neonatal melatonin treatment on the basal and thyrotropin or melatonin modified blood thyroxine level of adult rats.

Neonatal melatonin treatment caused a significant increase in thyroxine (T4) level at one month of age. Preexposure to melatonin in neonatal age and reexposure after one month accounted for a still greater increase in T4 production. Rats neonatally exposed to melatonin did not respond to TSH at one month of age.

The effect of bacterial endotoxin of phagocytosis of Tetrahymena and serotonin induced imprinting.

Endotoxin inhibited the phagocytosis of Tetrahymena pyriformis after a short exposure and, to a lesser degree, after repeated treatments during one week (about 35 generations). Endotoxin also prevented the development of serotonin imprinting. Detoxified endotoxin (Tolerin) affected the phagocytosis of Tetrahymena much less, indicating that the lipid-A part of the molecule may account for the membrane-toxic effect.

Influence of the neonatal suppression of TSH production (neonatal hyperthyroidism) on response to TSH in adulthood.

Six-day treatment of neonatal rats with T3 or T4 resulted in a considerable depression of T4 production in response to exogenous TSH in adulthood. This supports the hypothetical conclusion that hormonal imprinting, i.e. the presence of the hormone and its interaction with the cell during the period of receptor maturation, is important for receptor amplification, which accounts for normal response to the hormone in adulthood.

Selective and/or overlapping effect of pituitary hormones (thyrotropin, gonadotropin) on serum thyroxin and testosterone level in newly hatched cockerels.

Follicle-stimulating hormone and thyrotropin administered perinatally to cockerels have an overlapping effect on the testis and on the thyroid gland. Both hormones when given in one single dose considerably increased the serum level of both thyroxin and testosterone. In the case of chronic treatment performed in the perinatal period, the thyroxin level will similarly increase, though to a smaller extent, while the testosterone level decreases. The experiments studying the direct effect on hormone secretion proved the overlapping effect of the hormones in the perinatal period.

Imprinting, digoxin uptake and storage in Tetrahymena.

Tetrahymenas after a single exposure to high concentration of digoxin, release glycoside into the culture medium even three days after removal of the drug. After nine or fifteen days, however, this effect subsides. Re-administration of digoxin causes the digoxin consumption (storage) of Tetrahymenas to increase. This observation indicates that the digoxin imprinting previously demonstrated in mammals occurs also in Tetrahymena. The experiments raise the possibility that also Tetrahymenas are capable of producing a digoxin-like substance detectable by radioimmunoassay.

The effect of endotoxin and radio-detoxified endotoxin on the serum T4 level of rats and response of their thyroid gland to exogenous TSH.

We have demonstrated that, while the shock-inducing dose of parent (toxic) endotoxin significantly decreases the serum T4 level of rats and inhibits the T4 response given to exogenous thyroid stimulating hormone (TSH), the radio-detoxified (60Co-gamma, 150 kGy) endotoxin preparation does not inhibit the response to exogenous TSH and decreases serum T4 level to a lesser extent than untreated endotoxin.

Influence of neonatal endotoxin treatment and hormonal imprinting on thyrotropin-induced thyroxin (T4) production of adult rats.

A single subtoxic dose of endotoxin given to newborn rats by the intraperitoneal route decreased the T4 level in adulthood. TSH administration 24 hours after the endotoxin treatment failed to abolish this effect but, in this case, the response to TSH provocation in adulthood exceeded even the control value.

Effect of thyrotropin (TSH) treatment on the responsiveness of the thyroid gland during endotoxin shock in adult rats.

The shock-inducing dose (1.0 omg/200 g i.v.) of bacterial endotoxin (E coli 089) significantly decreased the serum levels of T4 and inhibited the T4 increasing action of thyrotropin in rats. It is suggested that the changes observed were due to the membrane damaging effect of endotoxin.