Growth hormone binding and stimulation of amino acid uptake in epithelial cells of rat ventral prostate

1. Net amino acid uptake, and incorporation into protein have been measured in vitro in the presence and absence of porcine growth hormone (GH) in muscle from intact rabbits fed for 5 d on low-protein (LP), protein-free (PF) or control diets.2. In muscle from control and LP animals GH had no effect on the net amino acid uptake but stimulated amino acid incorporation into protein, although this response was less in LP animals than in control animals.3. In muscle from PF animals, GH stimulated both amino acid incorporation into protein and the net amino acid uptake, a type of response which also occurs in hypophysectomized animals. The magnitude of the effect of GH on the incorporation of amino acids into protein was reduced in muscle from PF animals.4. The effect of GH on the net amino acid uptake in PF animals was completely blocked by cycloheximide; the uptake effect of GH in these animals was dependent therefore on de novo protein synthesis.5. It is proposed that in the adult the role of growth hormone in protein metabolism is to sustain cellular protein synthesis when there is a decrease in the level of substrate amino acids, similar to that which occurs during a short-term fast or when the dietary protein intake is inadequate.

Download Full-text

Action of insulin and growth hormone on protein synthesis in muscle from non-hypophysectomized rabbits

Biochemical Journal ◽

10.1042/bj1250515 ◽

1971 ◽

Vol 125 (2) ◽

pp. 515-520 ◽

Cited By ~ 13

Author(s):

P. J. Reeds ◽

K. A. Munday ◽

M. R. Turner

Keyword(s):

Amino Acids ◽

Growth Hormone ◽

Protein Synthesis ◽

Amino Acid ◽

Incubation Medium ◽

Amino Acid Uptake ◽

Diaphragm Muscle ◽

Acid Uptake

The separate effects of insulin and growth hormone on the uptake and incorporation of five amino acids into diaphragm muscle from non-hypophysectomized rabbits has been examined. Both growth hormone and insulin, when present in the medium separately, stimulated the incorporation into protein of the amino acids, leucine, arginine, valine, lysine and histidine. Insulin also stimulated amino acid uptake, but growth hormone did not. When insulin and growth hormone were present in the incubation medium together, the uptake and incorporation of valine, the only amino acid studied under these conditions, tended to be greater than the sum of the separate effects of the two hormones.

Download Full-text

Structural disruption of the trans-Golgi network does not interfere with the acute stimulation of glucose and amino acid uptake by insulin-like growth factor I in muscle cells

Biochemical Journal ◽

10.1042/bj2970289 ◽

1994 ◽

Vol 297 (2) ◽

pp. 289-295 ◽

Cited By ~ 22

Author(s):

H S Hundal ◽

P J Bilan ◽

T Tsakiridis ◽

A Marette ◽

A Klip

Keyword(s):

Amino Acid ◽

Brefeldin A ◽

Glucose Transporters ◽

Amino Acid Uptake ◽

Acid Uptake ◽

Trans Golgi Network ◽

Maximal Activation ◽

Igf I ◽

Golgi Network ◽

Stimulation Of

The effects of insulin-like growth factor I (IGF-I) on glucose and amino acid uptake were investigated in fully differentiated L6 muscle cells, in order to determine whether the two processes are functionally related. Transport of both glucose and amino acid (methylaminoisobutyric acid, MeAIB) was activated rapidly in response to IGF-I. Stimulation reached a peak within 30 min and was sustained for up to 90 min. Maximal activation of either glucose or MeAIB transport was achieved at 3 nM IGF-I; the half-maximal activation (ED50) of glucose transport was at 107 pM and that of MeAIB transport was at 36 pM. Stimulation of amino acid uptake occurred in the absence or presence of glucose, suggesting that this response is not secondary to increased glucose intake. Incubation of cells for 1 h with Brefeldin A (5 micrograms/ml), which disassembles the Golgi apparatus and inhibits the secretory pathway in eukaryotic cells, had no effect on the acute IGF-I activation of glucose and MeAIB transport. Moreover, Brefeldin A caused wide redistribution of the trans-Golgi antigen TGN38, as assessed by subcellular fractionation, without affecting the distribution of glucose transporters. The finding that the degree of activation, time response and sensitivity to IGF-I and Brefeldin A were similar for both glucose and MeAIB transport suggests commonalities in the IGF-I mechanism of recruitment of glucose transporters and stimulation of amino acid transport through System A. An integral trans-Golgi network does not appear to be required for the acute IGF-I stimulation of glucose or amino acid transport, even though stimulation of glucose transport occurs through recruitment of glucose transporters from intracellular stores in these cells. We propose that the donor site of glucose transporters (and perhaps of amino acid transporters) involved in the acute response to IGF-I lies beyond the trans-Golgi network, perhaps in an endosomal compartment in close proximity to the plasma membrane.

Download Full-text