Comparison of In Vitro Response to Growth Hormone by Chondrocytes from Mandibular Condyle Cartilage of Young and Old Mice

ABSTRACT The effect of growth hormone (GH) in vitro on the rate of intracellular accumulation of the non-utilizable amino acid α-aminoisobutyric acid (AIB) was studied in the intact rat diaphragm preparation. Bovine or ovine GH (25 μg/ml incubation medium) markedly stimulated the accumulation of AIB-14C by diaphragms from hypophysectomized rats, while there was no or only a very slight effect on diaphragms from normal rats. In diaphragms from rats with the pituitary gland autotransplanted to the kidney capsule GH in vitro stimulated the accumulation of AIB-14C significantly more than in diaphragms from normal rats but significantly less than in diaphragms from hypophysectomized rats. Injections of GH intramuscularly for 4 days to hypophysectomized rats made the diaphragms from these rats less sensitive or completely insensitive to GH in vitro. These results indicate strongly that the relative insensitivity to GH in vitro of diaphragms from normal rats is due to the fact that the muscle tissues from these rats has been exposed to the endogenously secreted GH. The results show that GH can influence the accumulation of AIB-14C in the isolated rat diaphragm in two different ways giving an acute or »stimulatory« effect and a late or »inhibitory« effect, and that it seems to be a time-relationship between these two effects of the hormone.

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ANALYSIS OF THE BIPHASIC ACTION OF GROWTH HORMONE IN VITRO ON THE RAT DIAPHRAGM

Acta Endocrinologica ◽

10.1530/acta.0.057s019 ◽

1968 ◽

Vol 57 (3_Suppl) ◽

pp. S19-S35 ◽

Cited By ~ 9

Author(s):

Å. Hjalmarson

Keyword(s):

Growth Hormone ◽

Actinomycin D ◽

Accumulation Rate ◽

Inhibitory Effect ◽

Bovine Growth Hormone ◽

Rat Diaphragm ◽

Dual Nature ◽

Hypophysectomized Rats ◽

D 20

ABSTRACT In vitro addition of bovine growth hormone (GH) to intact hemidiaphragms from hypophysectomized rats has previously been found to produce both an early stimulatory effect lasting for 2—3 hours and a subsequent late inhibitory effect during which the muscle is insensitive to further addition of GH (Hjalmarson 1968). These effects on the accumulation rate of α-aminoisobutyric acid (AIB) and D-xylose have been further studied. In presence of actinomycin D (20 μg/ml) or puromycin (100 μg/ml) the duration of the stimulatory effect of GH (25 μg/ml) was prolonged to last for at least 4—5 hours and the late inhibitory effect was prevented. Similar results were obtained when glucose-free incubation medium was used. Preincubation of the diaphragm at different glucose concentrations (0—5 mg/ml) for 3 hours did not change the GH sensitivity. Addition of insulin at start of incubation could not prevent GH from inducing its late inhibitory effect, while dexamethasone seemed to potentiate this effect of GH. Furthermore, adrenaline was found to decrease the uptake of AIB-14C and D-xylose-14C in the diaphragm, but not to change the sensitivity of the muscle to GH. Preincubation of the diaphragm for 3 hours with puromycin in a concentration of 200 μg/ml markedly decreased the subsequent basal uptake of both AIB-14C and D-xylose-14C, in the presence of puromycin, and abolished the stimulatory effect of GH on the accumulation of AIB-14C. However, the effect of GH on the accumulation of D-xylose-14C was unchanged. The present observations are discussed and evaluated in relation to various mechanisms of GH action proposed to explain the dual nature of the hormone.

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FACTORS AFFECTING THE REGENERATION OF PEPPER (CAPSICUM ANNUUM L.)

HortScience ◽

10.21273/hortsci.25.9.1120 ◽

1990 ◽

Vol 25 (9) ◽

pp. 1120G-1120

Author(s):

J. L. Jacobs ◽

C. T. Stephens

Keyword(s):

Growth Hormone ◽

Silver Nitrate ◽

Callus Formation ◽

Leaf Explants ◽

Regeneration System ◽

Factors Affecting ◽

Nitrate Concentrations ◽

Leaf Differentiation ◽

Whole Plants

Several growth hormone combinations and silver nitrate concentrations were examined for their effect on regeneration of different pepper genotypes. Primary leaf explants from in vitro seedlings were cultured on a revised Murashige and Skoog medium supplemented with auxin, cytokinin and 1.6% glucose. Combinations of different concentrations of indole-3-acetic acid (IAA), 0-5 mg/l, and 6-benzylaminopurine (BAP), 0-5 mg/l, were tested to determine the most effective medium for shoot primordium formation. Experiments with IAA and BAP did not result in a specific growth hormone combination appropriate for regeneration of all genotypes tested. Of the silver nitrate concentrations tested, 10 mg/l resulted in the best shoot and leaf differentiation and reduced callus formation. Differences in organogenic response of individual genotypes were evaluated on a single regeneration medium. Whole plants were regenerated from 11 of 63 genotypes examined. Based on these experiments, a reproducible regeneration system for pepper was developed with a total of 500 plants regenerated to date.

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