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Staffan Edén, Kerstin Albertsson-Wikland and Olle Isaksson

ABSTRACT

Radioimmunoassayable growth hormone (GH) was determined in fed and fasted female rats of different ages. In 6–40 day-old rats blood was collected at hourly intervals in groups of rats at different time intervals during the day. Within each age group the variation in plasma GH was considerable. In 6–14 day-old rats plasma GH was generally elevated. By day 18 levels declined, lowest on day 22 and by day 26 again increasing. In 14 day-old rats the median plasma level of GH was 22 ng/ml, in 22 day-old rats < 5 ng/ml and in 40 day-old rats 43 ng/ml. In 14 day-old rats levels ranged from < 5 ng/ml – 148 ng/ml, in 22 day-old rats from < 5 ng/ml – 34 ng/ml and in 40 day-old rats from < 5 ng/ml – > 200 ng/ml. A 20 h fasting period was associated with a significant decrease in plasma GH. In 45 day-old rats, the variations in plasma GH of individual animals were studied by obtaining sequential blood samples from unrestrained, undisturbed animals with implanted intra-aortic cannulae. In these rats GH secretion was characterized by an episodic release, occurring every 2–4 h. After a 20 h fasting period major peaks were depressed and occurred less frequently. It is concluded that there is an age-related as well as a circadian rhythm in growth hormone secretion in the rat and that sequential sampling of blood is essential for the evaluation of the secretory pattern.

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Staffan Edén, Kerstin Albertsson-Wikland, Sten Rosberg and Olle Isaksson

ABSTRACT

The effects of insulin and adrenaline on cyclic AMP (cAMP) levels in diaphragms of normal, streptozotocin-diabetic and insulin-treated diabetic rats were studied. Adrenaline caused a biphasic rise in cAMP with peak values of cAMP within the first few minutes. Diaphragms of diabetic rats showed an increased responsiveness to adrenaline. Injection of insulin to diabetic rats normalized the rise in cAMP after addition of adrenaline. There was no difference in basal levels of cAMP between diaphragms of normal, diabetic or insulin-treated diabetic rats. Insulin in vitro did not affect basal cAMP-levels or the release of cAMP from the tissue but significantly decreased adrenaline-induced peak levels of cAMP. This effect of insulin was abolished by theophylline.

The results of the present study suggest that experimental diabetes is associated with changes of the adenylate cyclase and/or phosphodiesterase enzyme activities in skeletal muscle resulting in an increased responsiveness to adrenaline. Since insulin in vitro depressed the adrenaline-induced elevation of cAMP the increased responsiveness in diaphragms of diabetic rats might be attributed to the specific lack of insulin.

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Görel Sundbeck, Staffan Edén, Rudolf Jagenburg and Göran Lindstedt

Abstract.

Serum TSH and free T4 were determined by chemiluminometric assays in 601 women and 285 men aged 85 years from the population study "70-year-old people in Gothenburg, Sweden". For individuals with serum TSH concentration above 6.0 mU/l, "antimicrosomal" antibodies were determined, to assess the etiology of the elevated TSH concentration. Clinical follow-up was done of survivors until the age of 88, and records were inspected also for individuals who died before that age. On the basis of these evaluations the prevalence of previously undetected hypothyroidism was estimated to 4.0% in women and 2.5% in men. Previously undetected hyperthyroidism was found in 2, at the most 4, out of 601 women; in one out of 285 men the diagnosis could not be excluded. Possible confounding factors for the evaluation of TSH and/or free T4 concentrations were analysed by permutation t-test followed by multiple regression analysis, which revealed correlations of log TSH concentration to body mass index (p<0.05), serum creatinine concentration (p<0.05), and diabetes mellitus (inverse relationship, p<0.01). Correlation was found of free T4 concentration to treatment with non-selective β-blocking agents (p<0.001) and digitalis glycosides (p<0.01). However, none of the factors influencing TSH and/or free T4 concentrations had any major influence on reference limits, nor could they account for individuals with "outlier" values.

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Eva Bagge, Staffan Edén, Thord Rosén and Bengt-Åke Bengtsson

The prevalence of radiographic osteoarthritis in hand and knee joints was studied in elderly patients with acromegaly and growth hormone deficiency, respectively, and compared with a normal population of elderly people. There were no major differences in the prevalence of osteoarthritis between the acromegalics and the normal population, but the patients with growth hormone deficiency had significantly (p<0.001) less osteoarthritis than the normal population. The lack of differences between the acromegalics and the normal population could be an effect of the age interval studied in which the prevalence of osteoarthritis is high. The low prevalence of osteoarthritis in patients with growth hormone deficiency suggests that growth hormone is an important factor in the development of osteoarthritis.

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John-Olov Jansson, Kerstin Albertsson-Wikland, Staffan Edén, Karl-Göran Thorngren and Olle Isaksson

Abstract.

The effect of frequency of growth hormone (GH) administration on longitudinal bone growth and body weight was studied in hypophysectomized rats which were given replacement therapy with corticosteroids, thyroxine and GH with start of therapy on the day of surgery. Longitudinal bone growth, as determined by the tetracycline method, was measured during the last 5 days of the 9 day long period with replacement therapy. The daily replacement dose of GH (bGH-17:NIH) was 200 μg and was given on 1, 2, 4 or 8 occasions.

Longitudinal bone growth was enhanced in the groups of animals receiving the hormone on two or more occasions per day. The most pronounced response was seen with an administration frequency of four times per day. Changes in body weight during the injection period showed similar changes.

The results of the present study show that the administration frequency of growth hormone is important for the growth rate in hypophysectomized rats which have been given replacement therapy. The findings suggest that the secretory pattern of GH is an important factor for optimum growth.

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Thord Rosén, Staffan Edén, Göran Larson, Lars Wilhelmsen and Bengt-Åke Bengtsson

Patients with adult onset growth hormone deficiency have a decreased life expectancy owing to an increased mortality from cardiovascular disease. In the present study, 104 subjects (66 men and 38 women, aged 22–74 years) with growth hormone deficiency and with adequate replacement therapy with glucocorticoids, thyroid hormones and gonadal steroids were studied with respect to known risk factors for cardiovascular disease. For comparison, data from a population study, "the MONICA study", were obtained. The patients had a significantly higher body mass index compared to controls (p<0.001). Serum triglyceride concentration was higher (p<0.001) but there was no difference in serum total cholesterol concentration. Serum high-density lipoprotein cholesterol concentration was lower (p<0.001) in the patients. There was no difference in the prevalence of diabetes mellitus. The prevalence of treated hypertension was higher (p<0.05) in the patients but the prevalence of smoking was lower (p <0.001). Even after taking the increased body mass index into consideration, the changes in the prevalence of treated hypertension (p<0.05) and in the serum concentrations of triglycerides (p<0.05) and high-density lipoprotein concentrations (p<0.001) remained. These results indicate that growth hormone deficiency alters lipoprotein metabolism and increases the risk for development of hypertension, which in turn might contribute to the increased risk for cardiovascular disease.

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Giovanni De Pergola, Xuefan Xu, Björn Carlsson, Peter Eriksson, Staffan Edén, Riccardo Giorgino and Per Björntorp

De Pergola G, Xu X, Carlsson B, Eriksson P, Edén S, Giorgino R, Björntorp P. Estradiol regulation of mRNA expression of stimulatory α-subunit in white adipose tissue from female rats. Eur J Endocrinol 1994;130:146–50. ISSN 0804–4643

Adipose tissue has been recognized as a major peripheral metabolic target of estrogens. The present study was addressed to examine in female rats whether differences in the adipose tissue mRNA expression of α-subunit of stimulatory (Gs) and/or inhibitory (Gj) G-proteins exist between intact and ovariectomized rats, the latter with or without estradiol or testosterone treatment. The fat cell membrane protein amount of Gs and Gj α-subunit also was examined. All these parameters were evaluated in parametrial fat tissue samples obtained from 40 female Sprague-Dawley rats. A group of rats (N=20) was investigated for evaluation of mRNA expression and another group (N=20) for quantification of the protein amount of Gs and Gj α-subunit. Each group was represented by five control rats (sham-operated), five ovariectomized (OVX) rats, five ovariectomized rats treated with estradiol (OVXE) and five ovariectomized rats treated with testosterone (OVXT). Ribonucleic acid extracted from adipose tissue and analyzed by northern blot with Gαs, Gαi-1 and Gαi-2 cRNA probes revealed three major bands with estimated sizes of 1.9, 3.5 and 2.35 kb, respectively. Messenger RNA quantitative analysis, by a solution of hybridization RNAase protection assay on total nucleic acid samples, showed that the amount of Gαi-1 and Gαi-2 mRNA was similar within the different groups, whereas the Gαs mRNA was significantly less abundant (p <0.01) in OVX and OVXT rats than in control or OVXE rats. No difference in Gαs mRNA content was found between control and OVXE rats. As with mRNA analysis, protein quantitative analysis by an enzyme-linked immunosorbent assay in fat cell membrane preparation showed that the amount of Gαi(1–2) was similar within the different groups and that the Gαs content was significantly higher in control and OVXE rats than in OVX and OVXT rats (p<0.01). This study in female rats shows that estradiol may be involved in the control of protein amount and mRNA expression of Gs α-subunit in adipose tissue. These results may explain in part how estrogens regulate the variations of body fat mass in female rats.

Giovanni De Pergola, via Putignani 236, 70122 Bari, Italy

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Staffan Edén, Bengt-Åke Bengtsson, Kerstin Albertsson-Wikland, Jörgen Elfversson, Göran Lindstedt, Per-Arne Lundberg, Björn Petruson and Sten Rosberg

Abstract. Profiles of plasma GH, plasma somatomedin-C and serum PRL concentrations as well as serum GH response to iv TRH were determined in 11 patients with acromegaly before and 10 days after surgery. Blood for profile determinations was drawn from a peripheral vein with a continuous withdrawal pump changing the recipient tube at 30-min intervals. Before surgery all patients had high plasma GH concentrations with irregular peaks and somatomedin-C concentrations were elevated. The response to TRH was abnormal in 8 patients. Three patients had slightly elevated PRL concentrations and one had high PRL concentration (6900 mU/l). Ten days after surgery GH concentrations were still high in 2 patients (>5 mU/l), as were somatomedin-C concentrations (3.2 and 2.4 U/l, respectively). In 3 patients basal GH concentrations were <5 mU/l and somatomedin-C concentrations were normal, but there were no major peaks in plasma GH concentrations. In 2 patients major peaks in GH concentrations appeared after surgery, but basal GH concentrations were 1.9 and 0.95 mU/l, respectively. One patient with hyperprolactinemia still had slightly elevated PRL concentration (486 mU/l), but the response to TRH was normalized. Finally, in 4 patients, mean GH concentrations were markedly reduced, somatomedin-C concentrations normalized and apparently normal plasma GH profiles appeared with low or undetectable basal levels separating major peaks. The results indicate that in some patients with acromegaly apparently normal GH secretion can be demonstrated 10 days postoperatively. Characterization of circadian GH rhythms during the early postoperative stage may contribute to the evaluation of the effect of surgery.

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Giovanni De Pergola, Xuefan Xu, Peter S Eriksson, Björn Carlsson, Ljang-Xiong Fu, Shumin Yang, Staffan Edén, Riccardo Giorgino and Per Björntorp

It has been the purpose of this study to examine possible differences in the amount of stimulatory (Gs) and inhibitory (Gi) G-protein α-subunits (measured with a quantitative enzyme-linked immunosorbent assay in fat cell membrane preparation) between subcutaneous and intra-abdominal regions in rats. The lipolytic response to isoproterenol and the number of β-adrenergic binding sites were also examined. These parameters were all evaluated simultaneously in subcutaneous (inguinal), epididymal and perirenal fat samples collected from six male Sprague-Dawley rats. The membrane contents of the Gs and Gi α-subunits were similar in the three depots. Moreover, no difference was found among the different regions with regard to isoproterenol-stimulated glycerol release and β-adrenoceptor number, expressed per cell number. In conclusion, the present study shows for the first time in rats that the abundance of inhibitory and stimulatory G-protein α-subunits is similar in subcutaneous and in visceral adipocytes. Moreover, the number ofβ-adrenoceptors and the lipolytic response to isoproterenol do not show significant variations with the anatomical site. As the present results are apparently in contrast with those obtained previously in human adipocytes, there is a possibility that the different results observed in rat and in human fat cells could be explained by species differences.