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.     

Investigation of gonadotropin-thyrotropin overlapping and hormonal imprinting in the rat testis

In the neonatal period both gonadotropin and thyrotropin increase the weight of the testis, influence considerably the diameter of the contorted tubules increase the occurrence of Sertoli cells and decrease the number of spermatogonia. These phenomena can still be observed at the age of seven days but they disappear by the age of six weeks; at that time the hormones decrease the weight of the testis. One single TSH treatment administered in the neonatal period considerably increased the weight of the testis and the diameter of the channels when investigated at the age of six weeks. Gonadotropin had none of these effects. The phenomenon of imprinting could be proved as in the animals pretreated with TSH, gonadotropin given at the age of six weeks decreased the weight of the testis and both hormones decreased the diameter of the seminiferous cords.     

Study of FSH-TSH functional overlap by cockerel testicle test

Comparison of the neonatal effects of FSH and TSH in the cockerel testicle test revealed that the latter caused a greater increase of testicular weight, tubular diameter and testicular interstital tissue. This finding suggests the possibility of FSH-TSH functional overlap during the perinatal critical period of receptor maturation.     

Impact of a single neonatal gonadotropin (FSH + LH) or thyrotropin (TSH) treatment on the sexual behaviour of the adult male rat

A single gonadotropin (FSH + LH) treatment of neonatal male rats resulted in depression of sexual activity in adulthood. It appears that not only steroids, but also gonadotropins may alter adult sexual behaviour by a single neonatal exposure. The chemically related hormone thyrotropin (TSH) had a similar, but much less pronounced, effect on adult sexual activity.     

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.     

Cyclosporine A inhibits the secretion of certain anterior pituitary hormones in patients with nephrotic syndrome.

To clarify the effects of cyclosporine A (CsA) on the secretion of serum thyrotropin (TSH), prolactin (PRL), luteinizing hormone (LH) and follicular stimulating hormone (FSH), we performed TRH and LH-RH testing in 4 patients with the nephrotic syndrome before and after the administration of CsA, 6 mg/kg/day for 4 to 12 weeks. Prior to CsA all patients responded normally to TRH with respect to TSH and PRL secretion. Two patients showed normal response of LH and FSH to LH-RH stimulation while the response in 2 other patients, who were both menopausal, was exaggerated. By the third or fourth week of CsA administration the basal and peak TSH and PRL values declined significantly in all patients in response to TRH stimulation while those of LH and FSH showed only a modest decrease in response to LH-RH stimulation. Two to 4 weeks after the cessation of CsA the response of TSH, PRL and FSH returned to the pretreatment level. These observations suggest that: 1) CsA exerts an inhibitory effect on the secretion of at least TSH and PRL in humans, and 2) the effect of CsA on the pituitary may be partially reversible after the cessation of the therapy.     

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.     

Hormonal imprinting and damages caused by fetal steroid treatment. Influence of fetal treatment with pregnancy-protecting steroids (allylestrenol, diethylstilbestrol) on the effect of gonadotropin administered to cockerels perinatally and at the age of six weeks

Single fetal (9th day) treatment with either diethylstilbestrol (DES) or allylestrenol (AE) caused a considerable decrease, both at the age of five days and six weeks, in the weight of the testicles and the diameter of the seminiferous cords, while the ratio of spermatogonia to primary spermatocytes increased. When measured either at the age of five days or six weeks, gonadotropin treatment [a combination of follicle stimulating hormone (FSH) and luteinizing hormone (LH)], administered twice daily for three days after the hatching, led to an increase in the above-mentioned parameter and to a shift in the cell ratio towards the control value. However, the absolute value of the controls treated with FSH-LH was by far not reached. The effect of perinatal treatment could be detected even in adulthood, namely, at the age of five days the response capability was relatively weak in the cockerels treated with DES and AE, while high responsiveness was observed at the age of six weeks. In some cases the relative value of the increment exceeded even that of the control; however in absolute term it was well below the control. On the basis of these experiments it might be concluded that hormonal imprinting evoked by FSH-LH treatment also occurs in the gonad damaged by DES and AE. The setting in of imprinting ameliorates the damages caused by DES and AE and increases the response capability of the cells.     

Hormonal imprinting in cell culture II. Evidence of hormonal imprinting and thyrotropin (TSH) -gonadotropin (FSH) overlap in a Chinese hamster ovary (CHO) cell line

Reexposure of cultures of the Chinese hamster ovarian cell line CHO K1 to FITC-labeled hormone 48 h after the first 24-h exposure to FSH or TSH showed that hormonal imprinting, accounting for a greater binding capacity on reexposure, also took place in in vitro conditions. TSH amplified the receptors of FSH to a greater degree than FSH itself, although the reverse effect failed to happen. TSH was able to bind the ovarian cells at first exposure, and to amplify the receptors for itself and--remarkably--to a considerably greater degree for FSH, exactly as observed earlier in in vivo systems.     

Impact of single neonatal allylestrenol treatment on the estrus cycle of rats treated with FSH+LH or TSH.

Neonatal allylestrenol treatment administered to female rats significantly increases the duration of estrus phase in the sexual cycle. Treatment with follicle stimulating hormone (FSH) + luteinizing hormone (LH) in adulthood prolongs the duration of estrus even on its own; the effect, however, is more pronounced in those animals who were treated (imprinted) with allylestrenol neonatally. When administered to the control animals, the chemically related thyreotrop hormone (TSH) is either indifferent or it even decreases the estrus index. In animals having received neonatal allylestrenol treatment, however, TSH administration increases significantly the duration of the estrus phase. Either with or without FSH+LH treatment, the ratio of estrogenic to gestagenic phase increases following neonatal allylestrenol treatment. The experiments call attention to the potential functional risks inherent in neonatal allylestrenol treatment. The actual risks, however, seem to be smaller than the effects seen at the receptor level.     

Age-dependent effect of Freund's adjuvant on 24-hour rhythms in plasma prolactin, growth hormone, thyrotropin, insulin, follicle-stimulating hormone, luteinizing hormone and testosterone in rats

The effect of Freund's adjuvant administration on 24-hour changes of plasma prolactin, growth hormone (GH), thyrotropin (TSH), insulin, follicle-stimulating hormone (FSH), luteinizing hormone (LH) and testosterone were studied in young (2 months) and aged (18 months) male Wistar rats. Rats were injected s.c. with Freund's adjuvant or adjuvant's vehicle and, 18 days later, they were killed at 6 different time intervals throughout a 24-hour cycle to measure circulating hormone levels by specific RIAs. Young rats receiving adjuvant's vehicle exhibited significant time-of-day-dependent variations in plasma TSH, LH and testosterone, with maximal levels at 1300 h, 0100 h and 1700 h, respectively. Prolactin and insulin levels, analyzed globally in a factorial ANOVA, showed significant time-of-day changes with maximal levels at 1300 - 1700 h and 2100 h, respectively. The daily rhythms in plasma LH and testosterone found in young rats were not longer observed in Freund's adjuvant-injected rats, while as far as TSH, a second peak was observed at 0100 h after Freund's adjuvant administration. Twenty-four hour rhythms in circulating TSH, LH and testosterone were blunted in old rats receiving either Freund's adjuvant or its vehicle. Aged rats exhibited significantly higher circulating levels of prolactin, and lower levels of GH, TSH, FSH and testosterone. The results indicate that secretion of prolactin, GH, TSH, FSH and testosterone are age-dependent, as are the responses of TSH, LH and testosterone to Freund's adjuvant administration.     

Interaction of thyrotropin (TSH) and gonadotropins in the function of genital organs. Effect of TSH and gonadotropin pretreatment (hormonal imprinting) of newborn rats on hormonal overlap in adult animals

At the age of 25 days the TSH-gonadotropin overlap is minimal in rats and extremely high doses of TSH are required to produce gonadotropin-like responses. Although the effect may be due also to some occasional contamination, nevertheless a single treatment of newborn animals (hormonal imprinting) with either hormone augmented the response to a second treatment with either hormone performed at 25 days of age. Newborn rats pretreated with either TSH or gonadotropin were exposed to a second TSH challenge at the age of 25 days exhibited responses which were not commeasurable to those observed after gonadotropin treatment alone. However, the amplifying action of TSH pretreatment with regard to the second response to gonadotropin was comparable or even more apparent than that of gonadotropin pretreatment.     

Influence of hormone concentration and time factor on TSH-FSH imprinting and overlap in CHO cells

Exposure of Chinese hamster ovarian cell cultures (cell line CHO) to TSH of FSH gave rise to hormonal imprinting. In earlier studies re-exposure after 48 h displayed a considerable increase in hormone binding. In the present experiments similar increase was demonstrated with an interval of five days. After 14 days, the increment was of lesser degree or even a decrease was noted in hormone-binding capacity. Although the CHO line originates from the target cells of gonadotropin, long-term positive imprinting was greater for TSH than for FSH, imprinting for FSH being negative rather than positive. The experimental results suggest that even very low concentrations (10(-13) mol) of hormone induce imprinting after an exposure as short as 60 min.     

Immunocytochemistry of the pituitary glycoprotein hormones.

The storage sites of the pituitary glycoprotein hormones were identified with the use of electron microscopic immunocytochemical techniques and antisera to the beta (beta) chains of follicle-stimulating hormone (FSH), luteinizing hormone (LH) and thyroid-stimulating hormone (TSH). The TSH cells in normal rats is ovoid or angular and contains small granules 60-160 nm in diameter. In TSH cells hypertrophied 45 days after thyroidectomy, staining is in globular patches in granules or diffusely distributed in the expanded profiles of dilated rough endoplasmic reticulum. The gonadotrophs (FSH and LH cells) exhibited three different morphologies. Type I cells are ovoid with a population of large granules and a population of small granules. Staining for FSHbeta or LHbeta was intense and specific only in the large granules (diameter of 400 nm or greater). Type II cells are angular or stellate and contain numerous secretory granules averaging 200-220 nm in diameter. They predominate during stages in the estrous cycle when FSH or LH secretion is high. Type III cells look like adrenocorticotropin (ACTH) cells in that they are stellate with peripherally arranged granules. They generally stain only with anti-FSHbeta and their staining can not be abolished by the addition of 100 ng ACTH. In preliminary quantitative studies of cycling females, we found that on serial sections FSH cells and LH cells show similar shifts to a more angular population of cells during stages of active secretion. However, the shifts are not in phase with one another. Furthermore, there are at least 1.5 times more FSH cells than LH cells at all stages of the cycle. Our collection of serial cells shows that some cells (usually type I or II) stain for both gonadotropic hormones, whereas others (usually type II or III) contain only one.     

Centrally applied somatostatin influences morphology of pituitary FSH cells but not FSH release

Effects of i.c.v. administered somatostatins on morphology and function of pituitary FSH cells were examined in adult male Wistar rats. The animals were given three 1 microg doses of SRIH-14 or SRIH-28 in 5 microl saline every second day. Controls were given the same volume of saline only. Both SRIH treatments lead to a significant decrease in absolute pituitary weight and volume of FSH cells in comparison with controls. Relative pituitary weight was significantly decreased only after SRIH-28 treatments, while FSH secretion was insignificantly decreased by both SRIH treatments. Our results indicate that i.c.v. applied somatostatins have significant inhibitory effect on absolute pituitary weight and on the volume of FSH cells, without affecting the hormone secretion in male rats.     

Effects of starvation and refeeding on gonadotropin and thyrotropin subunit mRNAs in male Japanese quail

The contents of mRNAs encoding LH beta-, FSH beta-, TSH beta- and common alpha-subunit precursor molecules were measured in food-deprived and subsequently re-fed male Japanese quail. Pituitary LH beta, FSH beta and common alpha mRNA levels were decreased by starvation, and increased to the control levels by re-feeding. The rates of decreases of LH beta and common alpha mRNA levels were greater the corresponding rate for FSH beta levels. Pituitary TSH beta mRNA levels were not decreased by starvation, but increased transitorily by re-feeding. Plasma LH and triiodothyronine levels were decreased by starvation, and then increased to control levels by re-feeding, while plasma FSH and thyroxine levels did not show significant changes. Plasma LH and FSH levels showed positive correlations with pituitary common alpha and FSH beta mRNA levels, respectively, while plasma thyroxine levels showed a negative correlation with TSH beta mRNA levels. Hepatic weight was decreased slightly but significantly by starvation, and then showed a remarkable rebound after re-feeding was started. These results suggest that LH synthesis and secretion are more sensitive to starvation than FSH synthesis and secretion in Japanese quail, and that LH production recovered to initial levels within several days when birds were fully fed. Also, there is a possibility that the synthesis of TSH is accelerated transitorily by re-feeding. Furthermore, these results showed that there are different relationships between the plasma levels of LH, FSH, and TSH and the various hormone subunit mRNA levels. The remarkable change in hepatic weight leads us to assume that hepatic thyroid hormone metabolism is affected by starvation and re-feeding.     

Influence of 50 Hz magnetic field on sex hormones and other fertility parameters of adult male rats

The effects of an extremely low frequency (ELF) magnetic field on the sex hormones and other fertility parameters of adult male Sprague-Dawley rats were investigated. Adult male rats were exposed to a 50 Hz sinusoidal magnetic field at approximately 25 microT (rms) for 18 consecutive weeks. There were no significant effects on the absolute body weight and the weight of the testes of the exposed rats. However, the weights of seminal vesicles and preputial glands were significantly reduced in the exposed male rats. Similarly, a significant reduction in sperm count was observed in the exposed group. Furthermore, there were no significant effects on the serum levels of male follicle stimulating hormone (FSH) during the 18 weeks of exposure period. On the other hand, there was a significant increase in the serum levels of male luteinizing hormone (LH) after 18 weeks of exposure (P < .005), while testosterone levels were significantly decreased only after 6 and 12 weeks of the exposure period. These results suggest that long term exposure to ELF could have adverse effects on mammalian fertility and reproduction.     

The involvement of cyclic-3',5'-AMP in the release of hormones from the anterior pituitary in vitro.

DBcAMP significantly increased the release of GH but not of LH, FSH, TSH, or PRL, except in the presence of hypothalamic extract when it augmented the release of LH, FSH, and GH, reversed the inhibition of PRL, but did not further influence TSH release. Theophylline increased release of GH and PRL while inducing increased tissue content of cAMP without consistently increasing the release of TSH, LH, or FSH. Hypothalamic extractor K+-stimulated hormone rel-ase was consistently and significantly potentiated by theophylline. Neither hypothalamic extract, increased [K+], or synthetic TRH and LRH were able to raise tissue content of cAMP while producing their expected effects on hormone release. Cholera enterotoxin produced a highly significant increase in tissue content of the cyclic nucleotide but increased the release of GH only, and not that of LH, FSH, TSH, or PRL. DBcAMP was able to lower the threshold concentration of K+ required to stimulate release of GH, LH, and FSH and also to augment K+-stimulated release to the higher levels induced by the hypothalamic releasing hormones. It did not augment K+-induced release of TSH.     

Comparison of pituitary responses to physical exercise in athletes and sedentary subjects

Serum growth hormone (GH), prolactin (PRL), cortisol, luteinizing hormone (LH), follicle-stimulating hormone (FSH) and thyroid-stimulating hormone (TSH) levels were evaluated before and after a bicycle ergometer exercise test in 8 male competitive volleyball players and in 8 sedentary healthy males of the same age. Increased serum GH and cortisol values after exercise in both groups were found, whereas an exercise-induced PRL release was observed in athletes only. Serum levels of LH, FSH and TSH were unaffected by the test in all subjects. A possible role of training in conditioning the hypothalamopituitary exercise-induced secretion is suggested.     

Pituitary hormones and growth retardation in rats raised at simulated high altitude (3800m).

Growth and the endocrine status of the pituitary and thyroid glands were studied in rats born and raised in a hypobaric chamber at a simulated high altitude of 3800 m (SHA); comparisons were drawn with similar rats at sea level. From birth until 40 days of age, SHA rats weighed significantly less than controls with the most striking growth impairment found in female SHA rats. Relative organ weights of anterior pituitary glands, ovaries and uteri from 40-day-old female SHA rats were significantly less than controls. Pituitary content of growth hormone (GH) was reduced in 40-day-old female SHA rats while the content of follicle-stimulating hormone (FSH) and luteinizing hormone (LH) were significantly increased over sea level controls. Plasma levels of GH, LH, FSH and thyrotropin (TSH) and pituitary TSH levels did not differ from control values. However, thyroidal uptake of 131I and plasma protein-bound 131I were significantly reduced in SHA rats as compared with controls. It is suggested that (1) the continuous exposure of developing female rats to hypoxia significantly impairs pituitary function and reproductive maturation, and (2) that despite other environmental factors acting on the developing organism at high altitude, growth retardation in rats born and raised at high altitudes is primarily a consequence of hypoxia.