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J Charrier

Publications and source records attributed to J Charrier.

41 records · Page 3Linked to original sources
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Growth hormone receptors in rat liver membranes: effects of fasting and refeeding, and correlation with plasma somatomedin activity.

The effects of fasting and refeeding on hepatic growth hormone receptors, on insulin receptors and on plasma somatomedin activity were studied. Female rats were either subjected to fasting for 4 days, refed for 3 days after a 4-day fasting, or allowed free access to food (controls). The specific binding of 125I-labelled bovine growth hormone was low in liver microsomal membranes (45% that of controls) and in plasma membranes (52% that of controls) of fasted rats. The number of somatotropic sites rather than the affinity of the binding was decreased. Lactogenic sites as judged by the binding of 125I-labelled human growth hormone were not significantly reduced in liver membranes of fasted rats. 125I-labelled insulin specific binding was enhanced in microsomal (184% that of controls) and plasma membranes (136% that of controls) of fasted rats; these modifications were associated with a decreased insulinemia. But immunoreactive rat growth hormone levels were not different in plasma of fasted, refed and control animals. Decreased plasma bioassayable somatomedin was associated with the low number of somatotropic binding sites in liver membranes of fasted rats. Somatomedin activity of refed animals was comparable to controls. A significant correlation between the plasma bioassayable somatomedin and the hepatic level of somatotropic binding sites was found. It is proposed that, in fasting, the loss of somatotropic binding sites in the liver is one of the possible causes of the decreased plasma somatomedin bioactivity.

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PubMedDate not supplied

In vivo effects of the GH-releasing heptapeptide GHRP-1 in lambs.

The novel synthetic growth hormone-releasing heptapeptide GHRP-1 is reported to be more potent than growth hormone-releasing hormone (GHRH) in eliciting GH release in vivo in rats and man. However, in ovine pituitary cells in primary culture in a perifusion system, GHRP-1 was 10-fold less active than GHRH. The purpose of this work was to study the effect of GHRP-1 in sheep in vivo. Ovine GH release stimulated by either GHRP-1 or GHRH(1-29)NH2, in eight pre-ruminant lambs, was determined. GHRP-1 was administered at doses of 1.2, 2.4 and 6 nmole/kg by i.v. bolus, and GHRH(1-29)NH2 at 0.3 nmole/kg. Mean+/-s.e.m. peak GH levels in the plasma after injection of saline, 1.2, 2.4, 6 nmole/kg GHRP-1 and 0.3 nmole/kg GHRH were 2.2+/-0.9, 9.3+/-2.5, 8.8+/-2.4, 35.1+/-5.8 and 51.6+/-10.5 ng/mL, respectively. As spontaneous 20 ng/mL peaks were observed, only peaks above this level can be considered as significant. The highest dose of GHRP-1 (6 nmole/kg) elicited oGH release, but its action was surpassed by GHRH 0.3 nmole/kg. Furthermore GHRP-1 and GHRH appear to behave inversely when response amplitudes are considered. Animals exhibiting a strong reaction to GHRH-1, show a correspondingly weak reaction to GHRH and vice-versa. This may reflect differences in intracellular mechanisms at the pituitary level. Our data support the results in vitro that in sheep GHRP-1 is a weaker stimulant of GH secretion than GHRH.

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