Thyrotropin-releasing hormone does not inhibit lysine vasopressin-induced growth hormone secretion in normal men

Summary In order to establish whether thyrotropin-releasing hormone (TRH) inhibits lysine-vasopressin (LVP)-induced growth hormone (GH) release, six normal men were tested with LVP alone or in combination with TRH. LVP strikingly increased serum GH levels; this response was not altered by TRH. These results indicated that in man TRH is not involved in the control of GH secretion in response to LVP.     

Thyrotropin-releasing hormone does not inhibit lysine vasopressin-induced growth hormone secretion in normal men

In order to establish whether thyrotropin-releasing hormone (TRH) inhibits lysine-vasopressin (LVP)-induced growth hormone (GH) release, six normal men were tested with LVP alone or in combination with TRH. LVP strikingly increased serum GH levels; this response was not altered by TRH. These results indicate that in man TRH is not involved in the control of GH secretion in response to LVP.     

Presence of thyrotropin-releasing hormone in porcine and bovine retina

Summary The thyrotropin-releasing hormone (TRH) has been found in porcine and in bovine retina, and it is indistinguishable from synthetic TRH in its immunological and biological properties. The role of retinal TRH is unknown, it probably acts as a neurotransmitter.     

Development and evaluation of a method of high pressure liquid chromatography for the determination of the level of degradation of thyroliberin (TRH) in blood]

The degradation of the TRH by plasma was studied using a sensitive method for the separation of TRH and products formed by high-pressure liquid chromatographic analysis (HPLC). The detected products are TRH-3H or synthetic TRH. The HPLC analysis is performed on a microparticulate (10 mu) silica gel chromatographic column with CH3CN/0,01 M NH4OAc, at pH 6 (30/70) (V/V). This technique provides a good separation of TRH and the other products of degradation. In our experimental conditions, the human plasma degrades 62.5 +/- 5% of of TRH in 60 mn; very similar results are obtained with thin layer chromatography.     

TRH analogue with C-terminal thioamide group. Synthesis,receptor binding,TSH-releasing activity and α-MSH-releasing activity

Summary A new TRH analogue containing a C-terminal thioamide group was synthesized. This peptide was shown to have receptor-binding affinity, and TSH- as well as -MSH-releasing activities very similar to native TRH.Acknowledgments. This work was supported by the Swedish Natural Science Research Council (K-KU 3020-112) and the Polish Academy of Sciences (Research Grant No. MR I 12.1.6.1).     

Control of pituitary secretion of melanotropin in an anuran amphibian by thyrotropin releasing factor (TRH). Study in vitro]

Intermediate lobes from Rana esculenta pituitary glands were continuously superfused for 7 hrs at 28 degrees C with amphibian culture medium. alpha-MSH release was measured by use of a sensitive double antibody radio-immunoassay system. alpha-MSH secretion was inhibited by low temperatures. A large increase in alpha-MSH release was observed when Thyrotropin Releasing Hormone (TRH) at doses ranging from 10(-9) to 10(-7) molar was added to the superfusion medium. Since large amounts of TRH are to be found in the hypothalamus of amphibians but have no effect over pituitary TSH secretion, the action of TRH over alpha-MSH release may have a physiological significance.     

Antagonism by thyrotropin-releasing hormone (TRH) of pentobarbital-induced hypothermia in rats with brain lesions

Summary Anesthesia with a large dose of pentobarbital (55 mg/kg, i.p.) caused a sustained decrease in brain temperature (Tb), which was monitored with a probe placed in the midbrain reticular formation. The administration of TRH to the lateral ventricle antagonized this hypothermia. None of the acute surgeries examined in this paper (adrenal-demedullectomy, septal knife cuts, electrolytic lesions of the hypothalamus and midbrain knife cuts) had any essential effect on this antagonism by TRH. These results suggest that centrally-administered TRH exerts its effect on thermoregulation, at least in part, through brain structure(s) caudal to the midbrain.     

Antagonism by thyrotropin-releasing hormone (TRH) of pentobarbital-induced hypothermia in rats with brain lesions

Anesthesia with a large dose of pentobarbital (55 mg/kg, i.p.) caused a sustained decrease in brain temperature (Tb), which was monitored with a probe placed in the midbrain reticular formation. The administration of TRH to the lateral ventricle antagonized this hypothermia. None of the acute surgeries examined in this paper (adrenal-demedullectomy, septal knife cuts, electrolytic lesions of the hypothalamus and midbrain knife cuts) had any essential effect on this antagonism by TRH. These results suggest that centrally-administered TRH exerts its effect on thermoregulation, at least in part, through brain structure(s) caudal to the midbrain.     

Effects of thyrotrophic-releasing hormone (TRH) on thermoregulation in the rat

At ambient temperatures (Ta) of both 8 and 22 degrees C, intraventricular administration of TRH (10-80 microgram) produced a dose-dependent hypothermia in rats. The hypothermia was due to both decreased metabolic heat production and cutaneous vasodilatation. In contrast, at 30 degrees C Ta, TRH increased metabolic heat production (due to behavioral excitation) and led to hyperthermia.     

Thermogenic effects of thyrotrophin-releasing hormone and its analogues in the rat

Acute or chronic injection of RX 77,368 (a TRH analogue; 1 mg/kg s.c.) stimulated oxygen consumption (VO2) and brown adipose tissue activity in the rat, and decreased weight gain. Other TRH analogues (CG 3509, RGH 2202) and TRH itself also stimulated VO2. These thermogenic actions are probably mediated centrally by stimulation of sympathetic outflow to brown fat.     

Distribution of thyrotropin releasing hormone (TRH), alpha-melanocyte-stimulating hormone (alpha-MSH) and somatostatin in the skin of the green frog (Rana esculenta)]

High concentrations of Thyrotrophin-Releasing Hormone (TRH) have been found in the dorsal skin of the Frog Rana esculenta, lower levels being measured in the ventral skin. alpha-MSH and somatostatin were undetectable in these tissues. Nor was TRH detected in the blood of these animals. The concentration of somatostatin in the pancreas was similar to that of the hypothalamus and twice or one hundred times higher than in the intestine or stomach respectively.     

Thermogenic effects of thyrotrophin-releasing hormone and its analogues in the rat

Summary Acute or chronic injection of RX 77368 (a TRH analogue; 1 mg/kg s.c.) stimulated oxygen consumption (VO₂) and brown adipose tissue activity in the rat, and decreased weight gain Other TRH analogues (CG 3509, RGH 2202) and TRH itself also stimulated VO₂. These thermogenic actions are probably mediated centrally by stimulation of sympathetic outflow to brown fat.     

Effects of thyroidectomy and thyroxine replacement on the responsiveness of the anterior pituitaries from male rats to thyrotropin-releasing hormone in vitro

Summary Thyroidectomy decreased prolactin concentrations in the anterior pituitary (AP) and serum of the male rat. The amount of basal and thyrotropin-releasing hormone (TRH)-stimulated release of prolactin by AP in vitro was lower in thyroidectomized (Tx) rats than in sham Tx rats. These results suggest that the inhibitory effects of thyroidectomy on pituitary and serum prolactin in male rats are mediated in part by the reduction of the production and spontaneous release of prolactin and the responsiveness of prolactin to TRH.     

Peptide-stimulated release of prolactin from the fowl anterior pituitary gland

Summary Anterior pituitary glands from broiler fowl were preincubated for 24 h in either medium 199 only or medium containing estradiol 17, following which they were incubated in medium containing thyrotrophin releasing hormone (TRH), vasoactive intestinal polypeptide (VIP) or substance P (SP), alone or with the dopamine agonist, apomorphine. Estradiol priming stimulated release of prolactin and enhanced apomorphine-inhibition of prolactin release. TRH stimulated prolactin release, an effect reversed by apomorphine, and priming with estradiol potentiated both effects. VIP stimulated prolactin to a lesser degree and again this was inhibited by apomorphine and potentiated by estradiol. SP had little effect on the nonsteroid-primed pituitary, but stimulated release of prolactin after estradiol treatment, though less effectively than TRH or VIP.     

A new type of antiserum to thyrotropin-releasing hormone; detection of new TRH-immunoreactive cell groups in rat hypothalamus

Summary We produced a new type of antiserum to thyrotropin-releasing hormone (TRH) in rabbits. The immunogen is TRH-BSA, the production of which is based on the formation of an amide bond using carbodiimide (EDC). The specificity of the antiserum was assessed by enzyme immunoassay (EIA) and immunohistochemistry. When using the anti-TRH serum for immunohistochemistry in rat hypothalamus, new magnocellular groups were detected in the ventrolateral parts of the posterior hypothalamus and the dorsal parts of the third ventricle. Colchicine treatment was found not to be necessary to visualize perikarya containing TRH.     

Mathematical model of pituitary thyrotropic function

Summary A nonlinear differential equation is used to develop a mathematical model describing the time course of thyrotropin (TSH) concentration in human plasma after thyroliberin (TRH) stimulation. The application of the model to real data shows that pituitary responsiveness to TRH is highest in euthyroidism, reduced in primary hypothyroidism, and lowest in hyperthyroidism.     

Hyperthermia after intrahypothalamic injections of thyrotropin releasing hormone (TRH) in the pigeon

Thermoregulatory responses to intrahypothalamic injections of thyrotropin releasing hormone (TRH) were recorded from unanesthetized pigeons exposed to 6 degrees C, 20 degrees C and 32 degrees C. Our results suggest that TRH is a non-specific excitatory neuromodulator or neurotransmitter for heat production in the pigeon.     

A new improved synthesis of thyrotropin releasing hormone

Summary This synthesis of thyrotropin releasing hormone (TRH) is particularly suitable for large scale production of highly purified TRH, thanks to its high yields of the coupling and deprotection reactions together with the very simple final purification step. The authors are indebted to Mr.I. Lalle for his excellent technical assistance.     

Intravenous thyrotropin releasing hormone (TRH) enhances the excitatory actions of acetylcholine (ACh) on rat cortical neurons

Summary I. v. administered TRH (1.25-10 mg/kg) enhanced the excitatory actions of iontophoretically applied ACh on spontaneously active cerebral cortical neurons of pentobarbital-anaesthetized rats. These observations are consistent with the hypothesis of a cholinergic-link in the anti-anaesthetic actions of exogenously administered TRH.     

Cholecystokinin-induced hypothermia in the rat

Summary Cholecystokinin-octapeptide (CCK-8) was shown to cause hypothermia after intracerebroventricular administration in the rat, and the hypothermic effect of CCK-8 was antagonized by simultaneous injection of TRH.