Increased growth hormone responses to growth hormone releasing hormone and thyrotropin releasing hormone in patients with metastatic testicular cancer

In 16 patients with metastatic testicular cancer and 10 age matched male control subjects growth hormone (GH) responses to growth hormone releasing hormone (GHRH; 1 microgram/kg body weight iv.) and thyrotropin releasing hormone (TRH; 200 micrograms iv.) were measured. Basal GH levels and GH levels following stimulation with GHRH or TRH were significantly increased in cancer patients compared to control subjects. 9 patients with testicular cancer were studied both in the stage of metastatic disease and after they had reached a complete remission. In complete remission GH responses to GHRH tended to decrease but the differences did not reach statistical significance. Our data suggest an alteration of hypothalamic and/or pituitary regulation of GH secretion in patients with metastatic testicular cancer.     

EOG responses in anesthetized freely breathing rats

In mammals, access of odor molecules to the olfactory receptor neurons is controlled by respiratory activity. Thus, anesthetized, freely breathing rats were used to record from the olfactory mucosa in the intact nasal cavity (electroolfactogram or EOG) so as to study global response characteristics to odor stimuli. During alternation of the inspiratory phases of odor sampling and expiratory phases, the response was a succession of individual EOG events synchronized with respiration. These were characterized by a steep decrease that started approximately 100-150 ms after the beginning of inhalation, reached its maximum at the transition between inspiration and expiration and was followed by a slower rise until the next inhalation. They were greater during the first respiratory cycles following odor stimulation onset. Thereafter their amplitudes decreased throughout odor delivery, but a significant EOG signal was still present at the end of short (10 s) and long (60 s) odor presentations. Amplitude increased with odor concentration, but much less than expected from concentration changes. Lastly, for some odors EOG responses persisted well beyond the end of stimulation. These results are in agreement with the respiratory synchronization of mitral cell activities observed during short odor presentations and long duration odor exposures. They underline again the importance of taking into account the respiratory activity in studies on the functioning of the olfactory system.     

Somatocrinin,growth hormone releasing factor,stimulates secretion of growth hormone in anesthetized rats

The synthetic replicate of a 44 amino acid peptide isolated from a human pancreatic tumor which had caused acromegaly possesses high specific activity to release growth hormone (GH) in anesthetized male rats. The GH secretion induced by this peptide is dose-dependent from 50 ng to 1 μg, with plasma GH concentrations increasing more than 10-fold within 5 min of iv administration at the higher doses. Two enzymatic degradation products of the 44 residue peptide were also isolated and consist of the first 37 and 40 amino acids. All three peptides appear to possess similar potency, on a molar basis, $\text{in}\text{vivo}$, contrary to $\text{in}\text{vitro}$ results. The specificity of these peptides on GH release was shown by their failure to alter plasma concentrations of prolactin (PRL), thyroid-stimulating hormone (TSH), luteinizing hormone (LH), follicle-stimulating hormone (FSH) and corticosterone. Based on these $\text{in}\text{vivo}$ results, the three peptides with serve as powerful tools with which to investigate the mechanisms of GH secretion.     

Growth hormone, thyrotropin and prolactin responses to simultaneous administration of human growth hormone-releasing factor and thyrotropin releasing hormone in the bovine

The effects of intravenous injection of synthetic human pancreatic growth hormone-releasing factor-44-NH2 (hpGRF-44) and synthetic thyrotropin releasing hormone (TRH), or hpGRF-44 in combination with TRH on growth hormone (GH), thyrotropin (TSH), and prolactin (PRL) release in dairy female calves (6- and 12-month-old) were studied. When 0.25 microgram of hpGRF-44 per kg of body weight (bw) was injected in combination with TRH (1.0 microgram per kg of bw), the mean plasma GH concentration of the 12-month-old calves rose to a maximum level of 191.5 ng/ml (P less than 0.001) at 15 min from the value of 6.8 ng/ml before injection at 0 min. The maximum level was 3.1 and 6.1 times as high as the peak values obtained after injection of hpGRF-44 (0.25 microgram per kg of bw) and TRH (1.0 microgram per kg of bw), respectively (P less than 0.001). The area under the GH response curve for the 12-month-old calves for 3 hr after injection of hpGRF-44 in combination with TRH was 2.5 times as large as the sum of the areas obtained by hpGRF-44 and TRH injections. In contrast, the mean plasma GH level was unchanged in saline injected calves. The magnitudes of the first and the second plasma GH responses in the 6-month-old calves to two consecutive injections of hpGRF-44 in combination with TRH at a 3-hr interval were very similar. The peak values of plasma GH in the calves after hpGRF-44 injection were 2-4 times as high as those after TRH injection.(ABSTRACT TRUNCATED AT 250 WORDS)     

Growth hormone and prolactin response to thyrotropin releasing hormone and growth hormone releasing factor in the immature turkey

Synthetic thyrotropin releasing hormone (TRH) and human pancreatic growth hormone releasing factor (hpGRF) stimulated growth hormone (GH) secretion in 6- to 9-week-old turkeys in a dose-related manner. TRH and hpGRF (1 and 10 micrograms/kg, respectively) each produced a sixfold increase in circulating GH levels 10 min after iv injection. Neither TRH nor hpGRF caused a substantial change in prolactin (PRL) secretion in unrestrained turkeys sampled through intraatrial cannulas. However, some significant increases in PRL levels, possibly related to stress, were noted.     

Plasma growth hormone responses to repetitive administrations of growth hormone releasing factor in patients with pituitary dwarfism

Plasma growth hormone (GH) responses to the repetitive administrations of synthetic human pancreatic growth hormone releasing factor (hpGRF-44) were studied in 15 patients with GH deficiency (11 diagnosed as idiopathic and 4 diagnosed as secondary to hypothalamo-pituitary tumor). hpGRF-44 was administered by single iv bolus (2 micrograms/kg), repetitive im (100 micrograms, twice a day), and/or repetitive iv infusion (2.5 micrograms/min for 90 min, once a day) for three to six consecutive days. Three of the eleven idiopathic GH deficient patients had plasma GH responses to both single iv bolus injection and repetitive administrations by im, or iv infusion of hpGRF. In four of the remaining eight, who had not had peak plasma GH levels above 5 ng/ml to a single iv bolus of the peptide, repetitive administrations of hpGRF-44 by im injection and/or iv infusion induced GH responses to the peptide. In the four patients with secondary GH deficiency, three had plasma GH response to hpGRF administration but one patient, who had indications of pituitary disorder, did not show any plasma GH response to either single iv injection or repetitive administrations of hpGRF-44. These data show that repetitive administrations of hpGRF-44 can induce plasma GH responses in some GH deficient patients who do not respond to a single iv bolus of the peptide.     

Enhanced growth hormone responses to growth hormone releasing hormone in male type I diabetic patients.

In a previous paper we have demonstrated that growth hormone (GH) responses to growth hormone releasing hormone (GHRH) are higher in premenopausal normal women than in age matched healthy men. As in type I diabetes mellitus various disturbances of GH secretion have been reported, the aim of our study was to assess the effect of sex on basal and GHRH stimulated GH secretion in type I diabetes mellitus. In 21 female and 23 male type I diabetic patients and 28 female and 30 male control subjects GH levels were measured before and after stimulation with GHRH (1 microgram/kg body weight i.v.) by radioimmunoassay. GH responses to GHRH were significantly higher in female than in male control subjects (p less than 0.02), whereas the GH levels following GHRH stimulation were similar in female and male type I diabetic patients. GH responses to GHRH were significantly higher in the male type I diabetic patients than in the male control subjects (p less than 0.001); in the female type I diabetic patients and the female control subjects, however, GH responses to GHRH were not statistically different. The absence of an effect of sex on GHRH stimulated GH responses in type I diabetes mellitus provides further evidence of an abnormal GH secretion in this disorder.     

Effects of corticotropin releasing factor and growth hormone releasing factor on pituitary hormone secretion in patients with congenital thyrotropin deficiency. Abnormal response of growth hormone to corticotropin releasing factor

Blood concentrations of anterior pituitary hormones, ACTH, GH, TSH, PRL, LH, and FSH were determined in corticotropin releasing factor (CRF) test (synthetic ovine CRF 1.0 microgram per kg body weight) and growth hormone releasing factor (GRF) test (synthetic human pancreatic GRF-44 100 micrograms) in 2 female sibling patients with congenital isolated TSH deficiency, in their mother, in 2 patients with congenital primary hypothyroidism and in 8 normal controls. The patients with isolated TSH deficiency showed normally increased plasma ACTH and serum GH after CRF and GRF, respectively, and also showed an abnormal GH response to CRF. The serum GH showed a rapid increase to maximum levels (12.9 ng/ml) within 30 to 60 min followed by decrease. The possibility of secretion of abnormal GH could be excluded by the fact that on serum dilution, GH value gave a linear plot passing through zero. In addition, serum PRL, LH and FSH levels after CRF administration in case 1 and PRL after GRF in case 2 were also slightly increased but these responses were marginal. The mother of the patients, patients with congenital primary hypothyroidism, and normal healthy controls showed normal responses of pituitary hormones throughout the experiment. Data from the present study and a previous report show that abnormal GH response to the hypothalamic hormones (CRF, TRH and LHRH) may be observed in patients with congenital isolated TSH deficiency.     

Behavioral effects of thyrotropin releasing hormone in frontal decorticated rats

A low dose intracerebroventricular injection of thyrotropin releasing hormone (TRH, 100 ng) changed many behavioral responses in the rat. TRH increased locomotion, scratching, body shaking, piloerection, and rearing, but decreased sniffing, and resting. Ablation of frontal neocortex further enhanced the TRH effects on locomotion and resting. A dose effect of TRH (0, 5, 10, 50, 100 ng) to increase general activity was established and the effect was further enhanced by decortication. In our test situations decortication had no effect by itself. Since the TRH effects became much more pronounced without the frontal neocortex it appears that the cortex exerts a powerful inhibitory effect to moderate the TRH effects. The TRH effect does not depend upon the frontal cortex, actually a cortical function is to dampen the TRH effects on various behavioral responses.     

Growth hormone response to thyrotropin releasing hormone in a pellagrin

An abnormal hyperresponse of GH to intravenous injection of TRH in a 66-year-old female pellagra patient with typical 3'D's was reported. Diagnosis of pellagra was mainly based on her clinical course and manifestations, although serum levels of nicotinic acid and serotonin were within the normal range. Serum vitamin A and B2 levels were low. However, these findings did not exclude the diagnosis. The abnormal GH response to TRH observed in this patient was decreased at 2 months and thoroughly disappeared at 10 months after admission. GH response to arginine showed an exaggerated and sustained response on admission, decreased at 2 months and showed an almost normal pattern at 10 months after admission. TSH and prolactin response to TRH were normal throughout the clinical course. LH and FSH response to LH-RH were exaggerated, suggesting post-menopausal hypogonadism. Cortisol response to ACTH showed slightly sustained reactions at both times of the provocation. Oral glucose tolerance test revealed a slight impairment in this patient. These results suggest that pellagra is one of the disorders which exhibit an abnormal hyperresponse of GH to intravenous administration of TRH.     

Plasma cortisol and growth hormone responses to intravenous characterization.

Plasma cortisol and growth hormone (HGH) responses to venous catheterization were studied in 29 volunteer subjects. Repeat characterizations were performed in 18 individuals. Mean plasma cortisol levels were significantly elevated during the first hour of the initial catheterization experience. Morning and afternoon levels of cortisol were not distinguishable during the first catheterization, but PM levels were significantly lower than AM levels during the second catheterization experience. Growth hormone responses were much more variable than cortisol and were distributed logarithmically. Growth hormone responses tended to parallel cortisol responses during the first catheterization experience. Individuals who listed more symptoms in response to venipuncture and catheterization after finishing their first catheterization had significantly higher cortisol and growth hormone levels during this experience. These data suggest a definite endocrine adaptation to catheterization by the second or third hour of the experience.     

Pituitary responsiveness to thyrotropin releasing hormone in insulin-dependent diabetes mellitus.

The pituitary responses to the intravenous administration of 200 mg of Thyrotropin Releasing Hormone were investigated in 14 poorly controlled insulin dependent diabetic males and in nine matched controls. The mean TSH and prolactin responses in the two groups were similar although both tended to be lower in the diabetics. There was a small FSH rise in 11 of the 23 subjects.     

Effect of thyrotropin releasing hormone injection on blood growth hormone (GH), TSH and growth hormone releasing hormone (GHRH) concentrations in cancer patients

In order to investigate whether endogenous GHRH and somatostatin were involved in the mechanism of the paradoxical GH rise after TRH injection, changes in serum GH and plasma GHRH were examined before and after TRH injection in 12 cancer patients and changes in serum TSH and GH were similarly studied in 76 cancer patients including 31 GH-responders and 45 GH-nonresponders to TRH. TRH stimulated GH secretions without altering the circulating GHRH concentration in 4 of the 12 cancer patients. There was neither a significant correlation between the increase from the basal to maximum GH and GHRH after TRH injection in the 12 cancer patients nor a reciprocal relationship between the increase in GH and TSH after TRH injection in the 76 cancer patients. These findings suggested that the paradoxical GH rise after TRH injection in cancer patients was exerted by its direct action at the pituitary level, and not mediated through the hypothalamus.     

Respiratory sinus arrhythmia in freely moving and anesthetized rats.

Heart rate increases during inspiration and slows during postinspiration; this respiratory sinus arrhythmia helps match pulmonary blood flow to lung inflation and maintain an appropriate diffusion gradient of oxygen in the lungs. This cardiorespiratory pattern is found in neonatal and adult humans, baboons, dogs, rabbits, and seals. Respiratory sinus arrhythmia occurs mainly due to inhibition of cardioinhibitory parasympathetic cardiac vagal neurons during inspiration. Surprisingly, however, a recent study in anesthetized rats paradoxically found an enhancement of cardiac vagal activity during inspiration, suggesting that rats have an inverted respiratory sinus arrhythmia (Rentero N, Cividjian A, Trevaks D, Pequignot JM, Quintin L, and McAllen RM. Am J Physiol Regul Integr Comp Physiol 283: R1327-R1334, 2002). To address this controversy, this study examined respiratory sinus arrhythmia in conscious freely moving rats and tested whether the commonly used experimental anesthetics urethane, pentobarbital sodium, or ketamine-xylazine alter respiratory sinus arrhythmia. Heart rate significantly increased 21 beats/min during inspiration in conscious rats, a pattern similar to the respiratory sinus arrhythmia that occurs in other species. However, anesthetics altered normal respiratory sinus arrhythmia. Ketamine-xylazine (87 mg/kg and 13 mg/kg) depressed and pentobarbital sodium (60 mg/kg) abolished normal respiratory sinus arrhythmia. Urethane (1 g/kg) inverted the cardiorespiratory pattern so that heart rate significantly decreased during inspiration. Our study demonstrates that heart rate normally increases during inspiration in conscious, freely moving rats, similar to the respiratory sinus arrhythmia pattern that occurs in other species but that this pattern is disrupted in the presence of general anesthetics, including inversion in the case of urethane. The presence and consequences of anesthetics need to be considered in studying the parasympathetic control of heart rate.     

Influence of prostaglandins and thyrotropin releasing hormone (TRH) on hormone secretion and growth in wether lambs.

A series of experiments were conducted in ewes and whether (castrate male) lambs to evaluate the influence of prostaglandins on secretion of anabolic hormones and to determine if repeated injections of prostaglandin (PG) F2alpha would chronically influence the secretion of these hormones and perhaps growth rate as well. A single intravenous injection of PGA1 and PGB1 (100 microgram/kg) exerted no significant (P greater than .10) influence on plasma concentrations of prolactin (PRL), growth hormone (GH) or thyrotropin (TSH) in ewes. PGA1, but not PGB1, stimulated an increase in the plasma concentration of insulin. Infusion of PGF2alpha for 5.5 hr into ewes resulted in increased (P less than .05) plasma concentrations of both GH and ARL while TSH and insulin were not significantly influenced. Prostaglandin F2alpha, when injected subcutaneously into wether lambs (10 mg twice weekly) stimulated (P less than .05) plasma GH concentrations after the first injection, but not after 3 weeks of treatment. Changes in plasma PRL or TSH were not observed consistently in the lambs treated chronically with PGF2alpha or TRH. Prostaglandin F2alpha, in the present studies, and PGE1 in previously reported studies (1-3), has been demonstrated to be stimulatory to the secretion of PRL and GH. In contrast, PGA1 and PGB1, which lack an 11-hydroxyl group, failed to influence the secretion of either PRL or GH. It would, therefore, appear that the 11-hydroxyl group is a structural requirement for prostaglandins to influence the secretion of these two hormones in sheep. Treatment with thyrotropin releasing hormone (TRH), alone or in combination with PGF 2alpha, significantly (P less than .05) increased growth rate (average daily gains) while PGF2alpha did not, despite the fact that both compounds exerted similar effects on plasma GH.     

Spinal cord thyrotropin releasing hormone receptors of morphine tolerant-dependent and abstinent rats

The effect of chronic administration of morphine and its withdrawal on the binding of 3H-[3-MeHis2]thyrotropin releasing hormone (3H-MeTRH) to membranes of the spinal cord of the rat was determined. Male Sprague-Dawley rats were implanted with either 6 placebo or 6 morphine pellets (each containing 75-mg morphine base) during a 7-day period. Two sets of animals were used. In one, the pellets were left intact at the time of sacrificing (tolerant-dependent) and in the other, the pellets were removed 16 hours prior to sacrificing (abstinent rats). In placebo-pellet-implanted rats, 3H-MeTRH bound to the spinal cord membranes at a single high affinity binding site with a Bmax of 21.3 +/- 1.6 fmol/mg protein, and an apparent dissociation constant Kd of 4.7 +/- 0.8 nM. In morphine tolerant-dependent or abstinent rats, the binding constants of 3H-MeTRH to spinal cord membranes were unaffected. Previous studies from this laboratory indicate that TRH can inhibit morphine tolerance-dependence and abstinence processes without modifying brain TRH receptors. Together with the present results, it appears that the inhibitory effect of TRH on morphine tolerance-dependence and abstinence is probably not mediated via central TRH receptors but may be due to its interaction with other neurotransmitter systems.