GROWTH HORMONE RELEASING FACTOR AND THE BIOASSAY-RADIOIMMUNOASSAY PARADOX REVISITED

1977 ◽  
Vol 86 (1) ◽  
pp. 71-80 ◽  
Author(s):  
Morton A. Vodian ◽  
Charles S. Nicoll
Keyword(s):  
Growth Hormone ◽  
Plasma Concentration ◽  
Quantitative Agreement ◽  
Biologically Active ◽  
Male Rats ◽  
Growth Hormone Releasing Factor ◽  
Granule Fraction ◽  
Rat Tibia ◽  
The Relationship

ABSTRACT Relationships between depletion of growth hormone (GH) from the rat adenohypophysis and its release into the circulation were re-evaluated using bioassay (BA: rat tibia test) and radioimmunoassay (RIA). Anaesthetized male rats were injected with a putative growth hormone releasing factor ("GRF") and killed 15 and 30 min later. For the assays, the plasma and adenohypophyses were pooled; the latter were separated into granule and cytosol fractions prior to assay. Fifteen minutes after "GRF" injection the BA recorded a 75 % depletion of GH from the granular fraction but the RIA measured a loss of only 13 %. By 30 min both assays recorded restoration of pituitary GH. Only slight changes occurred in the levels of BA- or RIA-detectable GH in the cytosol fractions. The massive depletion of bioassayable GH from the granule fraction was accompanied by a large increase (3.2 mU/ml) in the plasma concentration of BA-detectable hormone by 15 min. The slight depletion of RIA-detectable GH that occurred during this time was associated with a meagre increase (0.05 mU/ml) in the plasma level of immunoreactive GH. The plasma concentration of BA- and RIA-detectable GH did not change significantly between 15 and 30 min. Analysis of the relationship between depletion of GH from the pituitary and its release into the extrapituitary compartment disclosed that the BA recordings of these events were in excellent quantitative agreement but RIA measurements were not. The results confirm that biologically active GH can be depleted from and released by the adenohypophysis in vivo independently of RIA-detectable GH.

scholarly journals In vivo uptake of [14C]leucine by skeletal muscle ribosomes after injury in rats fed two levels of protein

1969 ◽  
Vol 23 (2) ◽  
pp. 271-280 ◽  
Author(s):  
V. R. Young ◽  
P. C. Huang
Keyword(s):  
Skeletal Muscle ◽  
Specific Activity ◽  
Male Rats ◽  
Thigh Muscle ◽  
Left Femur ◽  
The Right ◽  
And Control ◽  
The Relationship ◽  
In Vivo Uptake

1. After 14 days on a diet containing 5 or 25% casein male rats received a fracture of the left femur. Four hours before they were killed the injured and control rats were injected with [1-14C]leucine; the incorporation of radioactivity into an isolated fraction of skeletal muscle ribosomes was studied 6, 12, 24, 48, 72, 96 and 228 h after injury.2. The incorporation of [14C]leucine into the ribosome fraction in right thigh muscles dropped to 40% of control values 72 h after fracture in well-nourished rats and after 96 h with diets containing 5 or 25%, casein.3. The specific activity of the trichloroacetic acid-soluble fraction of muscle from injured rats was equal to or higher than that of the controls during the first 72 h but lower at 96 h.4. These results suggest that a reduced incorporation of amino acids by ribosomes from the right thigh muscle occurred on day 3 after fracture in the group receiving 25% casein but not in the group receiving 5% casein.5. Muscle RNA and DNA concentrations were not affected by the injury.6. The relationship between these findings and the loss of muscle N after injury is discussed.

Periodic interactions of GH-releasing factor and somatostatin can augment GH release in vitro

1987 ◽  
Vol 253 (5) ◽  
pp. E508-E514
Author(s):  
J. Weiss ◽  
M. J. Cronin ◽  
M. O. Thorner
Keyword(s):  
Growth Hormone ◽  
Human Growth Hormone ◽  
Human Growth ◽  
Male Rat ◽  
Base Line ◽  
Additive Effects ◽  
Growth Hormone Releasing Factor ◽  
The Impact

Growth hormone (GH) is secreted as pulses in vivo. To understand the signals governing this periodicity, we have established a perifusion-based model of pulsatile GH release. Male rat anterior pituitaries were dispersed and perifused with pulses of human growth hormone-releasing factor-(1--40) (GHRF), with or without a continuous or discontinuous somatostatin tonus. An experiment was composed of a 1-h base-line collection followed by four 3-h cycles; each contained single or paired 10-min infusion(s) of 3 nM GHRF. In testing the impact of somatostatin, the protocol was identical except that 0.3 nM somatostatin was added 30 min into the base-line period and then was either continued throughout the study or withdrawn during the periods of GHRF infusion. GH base lines with somatostatin were lower than vehicle base lines (P less than 0.05). GHRF pulses generated consistent peaks of GH release between 200 and 300 ng. min-1. (10(7) cells)-1, and these peaks were not altered by continuous somatostatin. In contrast, withdrawal of somatostatin during GHRF administration elicited markedly higher GH peaks (P less than 0.05) and more total GH release (P less than 0.05). This response could not be accounted for by the additive effects of GHRF and somatostatin withdrawal.

Immunoreactive and Biologically Active Growth Hormone-Releasing Factor in the Rat Placenta*

Endocrinology ◽  
1985 ◽  
Vol 117 (4) ◽  
pp. 1598-1601 ◽  
Author(s):  
ANDREW BAIRD ◽  
WILLIAM B. WEHRENBERG ◽  
PETER BÖHLEN ◽  
NICHOLAS LING
Keyword(s):  
Growth Hormone ◽  
Biologically Active ◽  
Active Growth ◽  
Growth Hormone Releasing Factor

Mechanism of action of Hexarelin. I. Growth hormone-releasing activity in the rat

1996 ◽  
Vol 135 (4) ◽  
pp. 481-488 ◽  
Author(s):  
Antonio Torsello ◽  
Roberta Grilli ◽  
Marina Luoni ◽  
Margherita Guidi ◽  
Maria Cristina Ghigo ◽  
...  
Keyword(s):  
Growth Hormone ◽  
Mechanism Of Action ◽  
Direct Action ◽  
Male Rats ◽  
Surgical Ablation ◽  
Adult Rats ◽  
Gh Secretion ◽  
Plasma Gh

Torsello A, Grilli R, Luoni M, Guidi M, Ghigo MC, Wehrenberg WB, Deghenghi R, Müller EE, Locatelli V. Mechanism of action of Hexarelin. I. Growth hormone-releasing activity in the rat. Eur J Endocrinol 1996;135:481–8. ISSN 0804–4643 We have reported Hexarelin (HEXA), an analog of growth hormone-releasing peptide 6 (GHRP-6), potently stimulates growth hormone (GH) secretion in infant and adult rats. This study was undertaken to further investigate Hexarelin's mechanisms of action. In 10-day-old pups, treatments with HEXA (80 μg/kg, b.i.d.) for 3–10 days significantly enhanced, in a time-related fashion, the GH response to an acute HEXA challenge. Qualitatively similar effects were elicited in pups passively immunized against growth hormone-releasing hormone (GHRH) from birth. In adult male rats, a 5-day pretreatment with HEXA (150 μg/kg, b.i.d.) did not enhance the effect of the acute challenge, and the same pattern was present after a 5-day pretreatment in male rats with surgical ablation of the mediobasal hypothalamus (MBH-ablated rats). In addition, in adult sham-operated rats, Hexarelin (300 μg/kg, iv) induced a GH response greater (p < 0.05) than that induced by GHRH (2 μg/kg, iv). However, in MBH-ablated rats 7 days after surgery, GHRH was significantly (p < 0.05) more effective than HEXA, and 30 days after surgery HEXA and GHRH evoked similar rises of plasma GH. Finally, the in vitro Hexarelin (10−6 mol/l) effect was transient while GHRH (10−8 mol/l) induced a longer lasting and greater GH release. Three different mechanisms, not mutually exclusive, are postulated for Hexarelin stimulation of GH secretion in vivo: a direct action on the pituitary, though of minor relevance; an indirect action that involves release of GHRH, of relevance only in adult rats; and an action through the release of a still unknown hypothalamic "factor", which in infant and adult rats elicits GH release acting sinergistically with GHRH. Antonio Torsello, Department of Pharmacology, via Vanvitelli 32, 20129 Milano, Italy

In vivo and in vitro evidence of growth hormone-releasing factor-like produced locally in the adenohypophyseal cells of the rat

Neuropeptides ◽  
1991 ◽  
Vol 19 (4) ◽  
pp. 223-229 ◽  
Author(s):  
J. Carretero ◽  
F. Sánchez ◽  
R. Vázquez ◽  
L. Cacicedo ◽  
F. Sánchez-Franco ◽  
...  
Keyword(s):  
Growth Hormone ◽  
Growth Hormone Releasing Factor

Potent interaction between glucocorticoids and growth hormone-releasing factor in vivo

Science ◽  
1983 ◽  
Vol 221 (4610) ◽  
pp. 556-558 ◽  
Author(s):  
W. Wehrenberg ◽  
A Baird ◽  
N Ling
Keyword(s):  
Growth Hormone ◽  
Growth Hormone Releasing Factor
Sign in / Sign up

Export Citation Format

Share Document