Serum Growth Hormone and Prolactin During and After the Development of the Obese-Hyperglycemic Syndrome in Mice

Larson, B. A.; Sinha, Y. N.; Vanderlaan, W. P.

doi:10.1210/endo-98-1-139

Cited by 61 publications

(23 citation statements)

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“…On the other hand, our results are not in keeping with those reported by Larson et al [1976] in male mice and by Seggie and Brown [1976] and Taya and lgarashi [ 1974] in male rats. Circadian rhythms in the secre tion of PRL were not found in all these investigations.…”

Section: Discussioncontrasting

confidence: 99%

Prolactin Secretion in Normal Male Mice during a Circadian Period

Dumm¹,

M²,

Estivariz³

et al. 1983

Cells Tissues Organs

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A quantitative ultrastructural study on the prolactin (PRL) cells of normal male mice was correlated with serum PRL immunoassay determination at different times in a circadian period. Significant time fluctuations in the percentages of cytoplasmic volume occupied by most of the organelles, as well as cyclic variations in serum PRL concentrations were detected. The endoplasmic reticulum appeared more developed at the beginning of the light period, suggesting a higher synthesis of PRL at this time. The evaluation of the Golgi complex and the secretory granules would indicate that packaging of secretory material and storing of PRL granules ccurred mainly during the second half of the light period. This coincided with the lowest values in serum PRL concentration and an increment in mitochondrial mass. The highest emiocytotic activity together with a diminution of total secretory granules were found during the dark period. The peak of PRL serum concentration was also present in this phase, but some hours later. Evaluation of microtubules and lysosomes gave some additional information. The results are in keeping with those from some biochemical investigations performed in mice and rats, but are not in agreement with others. The importance of a morphometric approach to evaluate and corroborate the immunoassay methods in the study of cyclic hormone secretion is emphasized.

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Section: Discussioncontrasting

confidence: 99%

Prolactin Secretion in Normal Male Mice during a Circadian Period

Dumm¹,

M²,

Estivariz³

et al. 1983

Cells Tissues Organs

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“…Because body mass index and several metabolic substrates have an effect on GH secretion [13], a relationship between leptin and GH has been investigated in several species including man. The genetically ob/ob mouse has reduced plasma GH levels [14]. In humans, Clement et al [15]recently found that a mutation of the leptin receptor gene caused obesity and a reduction in GH secretion.…”

Section: Discussionmentioning

confidence: 99%

The in vitro Effect of Leptin onBasal and Growth Hormone-Releasing Hormone-StimulatedGrowth Hormone Secretion from theOvine Pituitary Gland

Roh

Clarke

et al. 1998

Neuroendocrinology

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We have studied the direct effect of leptin on the secretion of GH from the anterior pituitary gland of the sheep. Using primary cultures of ovine pituitary cells, leptin (10^–9–10^–7 M) treatment for 30 min did not affect basal or GHRH (10^–7 M)-stimulated GH secretion. Following treatment for 24 h, a dose of 10^–7 M leptin stimulated basal GH secretion. In contrast, doses of 10^–7 and 10^–8 M leptin inhibited GHRH-stimulated GH secretion after 24 h of treatment. These results suggest that leptin can have long-term effects on the somatotropes, but no acute effect. Furthermore, leptin appears to have opposite effects on basal and GHRH-stimulated GH secretion.

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“…Thyroxine levels are depressed in 6-20-day-old ob/ob mice [31], although they are normal after weaning [32]. Circulating growth hormone is reported to be normal [33] or decreased [34] in obese mice, but may not contribute to the decrease in skeletal musculature since plasma somatomedin concentration is normal [35]. It could be argued also that the marked hypoactivity of obese mice may trigger a reduction in size of their presumably less frequently used fast twitch skeletal muscle fibres.…”

Section: Discussionmentioning

confidence: 99%

A histochemical and morphological study of skeletal muscle from obese hyperglycaemic ob/ob mice

almond

Enser

1984

Diabetologia

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Summary. The histochemical and morphological charactefis= tics of muscles from lean and obese hyperglycaemic ob/ob mice were compared to determine the nature of the low skeletal muscle mass of the latter: Gastrocnemius and biceps brachii muscles from obese ob/ob mice were significantly lighter than those from lean mice; whereas the weights of soleus muscles were not significantly different. The small mass of the biceps brachii muscle resulted from a decrease in diameter of the large glycolytic fast white and fast intermediate fibres and a reduction in the proportion of fast white fibres.The size and frequency of the more oxidative fast red fibres was not different. The histochemical appearance of all fibre types studied from muscles in obese mice was identical to equivalent fibres in lean mice. The fat content of muscles from obese mice was three times greater than in lean mice whereas muscle DNA concentration was similar.Key words: Obese mice, muscle size, fibre type, fibre number, diabetes.Obese hyperglycaemic mice with the ob/ob genome have been used extensively as a model for Type 2 (noninsulin-dependent) diabetes. They are characterized by many abnormalities including hyperphagia, fasting hyperglycaemia, and hyperinsulinaemia. They have fewer insulin receptors and their tissues, particularly muscle, show a marked resistance to the normal metabolic actions of this hormone [1]. Obese mice have similar quantities of total body protein to lean mice [2]. However, extra protein present in their enlarged adipose tissue, liver, and intestine disguises a lower content of skeletal muscle protein [3,4].The smaller amount of muscle could be due to a decrease in the number of muscle fibres, or a reduced volume per fibre, or both. If there were fewer fibres within the muscles of obese mice, it would indicate a difference in pre-natat development compared with lean mice since in mice the majority of muscle fibres are present at or soon after birth [5, 6]-On the other hand, a decrease in the post-natal growth of fibres would be compatible with the other reported metabolic defects in ob/ob mice. Insulin is probably the most important physiological factor regulating the overall protein balance in skeletal muscle [7] since k not only stimulates the uptake of amino-acids and protein synthesis, [8] but also inhibits protein degradation. It is conceivable, therefore, that the inherent resistance of muscles from obese mice to the anabolic effects of insulin [9,10] could facilitate a decrease in the post-natal growth of this tissue. Plasma corticosteroid levels are also elevated in ob/ob mice [11,12] and may cause accelerated protein degradation and diversion of amino-acids into excessive gluconeogenesis [13]. If these metabolic abnormalities in obese mice are responsible for their decreased skeletal muscle mass, one would predict that fast and slow phasic muscles would respond differently, since either st~eptozotocin-induced diabetes [14] or corticosteroid injections in rats [15] cause large glycolytic fibres and fast phasic musc...

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Serum Growth Hormone and Prolactin During and After the Development of the Obese-Hyperglycemic Syndrome in Mice

Cited by 61 publications

References 0 publications

Prolactin Secretion in Normal Male Mice during a Circadian Period

Prolactin Secretion in Normal Male Mice during a Circadian Period

The in vitro Effect of Leptin onBasal and Growth Hormone-Releasing Hormone-StimulatedGrowth Hormone Secretion from theOvine Pituitary Gland

A histochemical and morphological study of skeletal muscle from obese hyperglycaemic ob/ob mice

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