L-triiodothyronine stimulates growth by means of an autocrine factor in a cultured growth-hormone-producing cell line.

L-Triiodothyronine (T3) stimulates DNA synthesis and replication of cultured GC cells, a T3-responsive growth hormone (GH)-secreting cell line. To determine whether T3 stimulates secretion of an autocrine growth factor, we compared the growth-promoting activity of medium conditioned by T3-stimulated and T3-depleted cells to that of unconditioned medium. Addition of polyclonal rabbit anti-T3 serum to T3-containing media decreased cellular T3 content by 50-70%. In unconditioned medium, anti-T3 serum decreased T3-induced cell growth and GH production by 40-70%. In conditioned medium, anti-T3 serum also effected a 45-70% decrease in induction of GH secretion but did not attenuate the growth-promoting activity. Growth-promoting activity was not detected in medium conditioned by T3-depleted cells. Thus, conditioned medium from T3-containing GC cell cultures contains growth-promoting activity that is independent of T3. Further, the induction of GC cel growth by T3 may occur, at least in part, by induction of an autocrine growth factor.

L-Triiodothyronine (T3) stimulates growth of cultured GC cells by action early in the G1 period: evidence for mediation by the nuclear T3 receptor.

Incubation with T3 results in a dose-dependent increase in growth rate of cultured GC cells, a GH-producing rat pituitary tumor cell line. The T3-induced increase in growth rate results mainly from shortening of the G1 period from 79.4 +/- 4.3 (SD) h in cells grown in T3-depleted medium (-T3) to 10.0 +/- 0.9 h. This effect can also be demonstrated in synchronized populations. Addition of T3 (0.3 nM) to cells synchronized in early G1 in the absence of T3 shortened the G1 period, estimated from graphic data, from more than 40-50 h to 13.4 +/- 2.1 h (n = 7). To determine the mechanism of this T3 effect, GC cells were grown in Dulbecco's modified Eagle's medium containing 10% serum plus or minus T3 (0.3 nM) and synchronized at the beginning of the G1 period by mitotic selection. Mitotic cells (85-100%), obtained by controlled mechanical shaking, were isolated by centrifugation and replated. The end of G1 was determined by the onset of DNA synthesis with [3H]thymidine as assessed by autoradiography (percent labeled nuclei). L-T3-induced shortening of G1 was detectable at 0.05 nM T3, half-maximal at physiological T3 (0.17 nM), and maximal between 0.3 nM and 1.0 nM T3. Addition of cycloheximide, 0.025 microgram/ml or 1.0 microgram/ml, decreased protein synthesis by 50% and 90%, respectively, and attenuated the T3 effect on G1 by 80-90%. The attenuation of the T3 effect on G1 by cycloheximide at a dose which inhibited protein synthesis suggests that T3-induced shortening of G1 may require new protein synthesis. Since glucocorticoids decrease the effect of T3 on induction of alpha-aminoisobutyric acid transport, their effect on T3-induced shortening of G1 was determined in G1-synchronized GC cells and in asynchronous cultures. Cortisol, 100 nM, significantly decreased the growth rate of asynchronous GC cells and attenuated the effect of T3 in G1-synchronized cells. Finally, T4 also decreased the length of G1 in a dose-dependent manner with a half-maximal effect at 40.0 nM. The half-maximal effect of T4 occurred at a nuclear iodothyronine concentration that was comparable to that achieved in incubations with 0.17 nM T3 (half-maximal dose). Thus, half-maximal shortening of G1 in synchronized GC cell cultures occurred at iodothyronine concentrations required for half-maximal occupancy of nuclear T3 receptors and for half-maximal induction of GH synthesis, growth rate, alpha-aminoisobutyric acid uptake, and depletion of the nuclear T3 receptor.(ABSTRACT TRUNCATED AT 400 WORDS)

Triiodothyronine stimulates growth of cultured GC cells by action early in the G1 period.

T3 regulates the proliferation rate of GC cells, a rat GH-secreting pituitary tumor cell line, by modulating the duration of the G1 period. In GC cells which were synchronized at the beginning of G1 by mitotic selection, the G1 period was 11.7 +/- (SE)2.1 h, in agreement with the value we obtained in asynchronous cells by other methods (10.0 +/- 0.9 h). G1 was significantly prolonged in synchronized GC cells, previously maintained in the absence of T3 for more than 1 cycle time. G1 duration decreased when cells were exposed to T3 only during a discrete 4-6 h interval early in G1. Thus, T3 appeared to stimulate progression through the G1 period by action early in G1.

The initial attitudes of patients toward longer maintenance hemodialysis.

UNLABELLED: Longer hemodialysis (HD) as practiced in parts of Europe and Japan may improve both blood pressure control and patient survival. Nevertheless, in the USA, the trend has been to shorten dialysis time using larger dialyzers and increased blood flows. Many patients find the notion of shorter dialysis enticing. Most are unaware ofthe potential benefits of longer dialysis. We surveyed stable chronic HD patients in an urban area, the vast majority of whom received conventional 4-hour treatments, regarding their attitude toward extending their dialysis time to 5 hours. They were informed that longer dialysis has been associated with better blood pressure control and improved survival. One hundred and sixteen patients completed questionnaires during a single dialysis session. Forty-six (40%) agreed to extended dialysis while 70 (60%) did not. There was no difference between the groups with respect to the following variables: age, race, etiology of ESRD, time on dialysis, marital status, number of children at home, number residing in the household, education, or employment status. Male gender was associated with a positive response (p = 0.03). Various suggested and spontaneous reasons were given for a negative response. CONCLUSION: With minimally detailed information, 4 in 10 patients were willing to extend their treatment time to 5 hours in the hope of improving morbidity and survival. No sociodemographic variable except gender was associated with a positive response.

[Hypophysial and ovarian function following a single postnatal estradiol injection. I. Studies by means of intrasplenic ovarian graft (author's transl)]. / Hypophysen- und Ovarienfunktion nach einer postnatalen Oestradiolinjektion I. Untersuchungen vermittels Ovarimplantats in Milz.

We have studied the development of the intrasplenic ovarian graft in rats which had received an injection of 100 microgram estradiol benzoate in the first days of life (estrogenized rats). We formed several groups consisting of autografts, homografts in females and males, normal ovarian graft in estrogenized rats and estrogenized ovarian graft in normal rats. In comparison with the results obtained in control groups (rats without postnatal injection), the frequency of luteinised grafts in all experimental groups is reduced by 50-100%. This phenomenon is due not only to the diminution of the hypophysial function but also to ovarian dysfunction, both processes produced by the postnatal estrogen injection.

[Hypophysian and ovarian function following a single postnatal estradiol injection. II. Studies on rats in parabiosis (author's transl)]. / Hypophysen- und Ovarienfunktion nach einer postnatalen Oestradiolinjektion II. Untersuchungen an Ratten in Parabiose.

We have studied the functioning of the axis hypophysis-ovary in rats which had received an injection of 100 microgram estradiol benzoate, in the first days of life. The experimental method was the parabiosis of two animals (male or female, normal or estrogenized, intact or spayed) in different combinations. We established that estrogenization damages the hypopysis as well as the ovary to such a degree that both glands cease to function normally. --Injected gonadotrophins can procude luteinization of estrogenized ovaries. This effect, however, appears only as a direct consequence of hormone administration. Exogenous gonadotrophins can never trigger cyclical function of estrogenized ovaries.

[Gonadal function of rats following pre- or postnatal administration of some hormones (author's transl)]. / Die Keimdrüsenfunktion der Ratte nach prae- oder postnataler Injektion verschiedener Hormone

Some steroid hormones as well as clomiphene have been administered to new-born rats (postnatally) or to pregnant rats (prenatally) in order to study the effect on the future gonadal function of the animals born before or after the injection. A single postnatal androgen injection in oily solution influences only the female function; estrogen or the combination of androgen and estrogen are effective in both sexes preventing the ovulation or damaging the testicles. If the hormone is administered in water instead of oil, several injections are necessary in order to obtain an effect. Only the aqueous solution of clomiphene produces a positive effect even given in a single injection. When a single postnatal injection is effective the same result can be obtained after prenatal administration but only following intraamniotic injection. Clomiphene is an exception to this rule; intraamniotic injection has no effect. These observations permit the following conclusions: 1. It is possible to influence the hypothalamus-hypophysis function not only in the first days of life but already in the prenatal period. 2. As androgen damages only the ovary, estrogen however the gonads of both sexes, the mechanisme of action can not be the same. Androgen alters the function of the sexual centres in the brain only in the female rat, estrogen paralyses this function in both sexes. 3. Prenatal injection of hormone is only effective if administered intraamniotically (eliminating in this way the action of the placenta). This proves the important role of the placenta in the metabolisme of the hormones. 4. Other possible consequences of postnatal androgen administration as permanent obstruction of the vagina or hypertrophy of the clitoris can be obtained equally by prenatal intraamniotic injection. These phenomena can also occur independent of the avarian processes, being due to direct hormonal action. 5. Tubo-ovarian inflammation and abscesses are observed with relative frequency especially following estrogen or clomiphene-administration. The cause is unknown but we can assume that circulatory disorders in the genital area, produced by the hormone, are responsible for the frequency of these phenomena.

PIP: Several studies researching the effect of hormonal administration on the gonadal functions of rats are correlated. Hormonal preparations that are administered in oily solutions affect gonadal functions only if the injection is postnatal or intraamniotic. This indicates that the placenta plays an important role in maintaining a hormonal balance for the fetus after the mother receives extraamniotic, sc, or ip injections. Hormonal injections administered in water solutions must be repeated to have an effect. Clomiphene will affect gonadal functions when injected postnatally, but not when injected intraamniotically; experiments show that this is not due to any effect of amniotic fluid or clomiphene. Postnatal injection of testosterone affects only female animals, which would indicate a transformation of the biphasic function of the sexual centers of the cerebrum. Estradiol affects both sexes, which seems to result from a paralysis of the biphasal function. Intraamniotic injection of hormones or immediate postnatal injection of testosterone will hinder the opening of the vagina and cause hypertrophy of the clitoris, which will not always coincide with anovulatory ovaries. This would indicate different causes for these various dysfunctions. Inflammation of the adnexa uteri often accompanies hormonal injections (especially estrogen and clomiphene), which is probably linked to disturbances in the genital circulatory system.

[Rat ovarian function after post or prenatal injection of clomiphen]. / Keimdrüsenfunktion der Ratte nach post- oder pränataler Injektion von Clomiphen

If newborn rats are subcutaneously injected with 0,075--0,100 mg of Clomiphene Citrate within the first 5 days, it results that 73.7% of the females remain anovulatory. The percentage rises to 100 if 0,125--0,400 mg are given in several injections. The identical treatment has no influence on the testicular function. Prenatal administration to pregnant rats (total amount 0,250--2,70 mg in repeated subcutaneous injections) interrupts the pregnancy in a high percentage, but has no effect on the later gonadal function of the foetuses. Equally ineffective is the prenatal intra-amniotic injection of clomiphene (0,125--0,250 mg into each amniotic cavity). In this respect the action of Clomiphene differs from the action of testosterone and also of estradiol, as these two hormones produce the identical effect after intra-amniotic as after postnatal administration i.e. they are effective if passage through the placenta is avoided. Clomiphene, postnatally effective, loses its effectiveness when intra-amniotically injected, although the placenta is eluded. An inactivating action of the amnion fluid could be the explanation of this phenomenon.

Induction of amino acid transport by L-triiodothyronine in cultured growth hormone-producing rat pituitary tumor cells (GC cells).

The action of L-triiodothyronine (T3) on amino acid transport in the GC clonal strain of rat pituitary cells was investigated by measurement of the uptake of the nonmetabolizable amino acid, alpha-aminoisobutyric acid (AIB). The uptake of AIB by GC cells appeared to require energy and Na+ and displayed Michaelis-Menten kinetics. In comparison to cultures maintained in the absence of T3, T3 addition resulted in an increase in AIB uptake which seemed due to an increase in the initial rate of AIB transport. T3 addition resulted in increased AIB accumulation at later time points as well. T3 induction of AIB transport did not occur until 3.5 h after addition of T3, and this effect was blocked by cycloheximide. Maximal induction occurred 48 to 72 h later. One-half maximal induction occurred 24 to 48 h after addition of T3. No detectable changes either in AIB uptake or intracellular water space, measured by uptake of the nonmetabolizable sugar, 3-O-methyl-D-glucose, were noted for the first 120 min after addition of T3. Induction of AIB transport occurred at 0.05 nM T3 (total medium concentration) and one-half maximal induction occurred at 0.17 nM T3. The relative potencies of four iodothyronine analogues for AIB transport were in accord with their reported activities in nuclear T3 receptor binding assays. These data suggest that induction of AIB transport by T3 may be mediated by the nuclear T3 receptor and may reflect the pleiotrophic response of GC cells to thyroid hormone.