Physiological importance of the T3 mitochondrial pathway.
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Biomedical subjects
Publications and source records attributed to A Fraysse.
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A 29 year old woman was hospitalized for the successive onset of extremely serious vascular accidents: rupture of the gastro-duodenal artery, aneurysm of the posterior tibial artery, discovery of bilateral carotid and vertebral aneurysm with development of a carotid-cavernous fistula. The patient had a very unusual morphotype with dwarfism, white hair and alopecia. Histological investigations failed to reveal atheromatous lesions and by contrast showed involvement of the skin (dermal atrophy) and in the blood vessels fibro-dysplasia of the media. This picture was suggestive of a vascular form of Ehlers-Danlos disease (Sack's syndrome or type IV Ehlers-Danlos disease). This syndrome is characterized by minor skin or joint manifestations replaced by arterial accidents (arterial rupture or development of aneurysms). The etiology is faulty maturation of procollagen III and the diagnosis is based upon fibroblast culture.
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.