Regulation of plasma and tissue levels of insulin-like growth factor-I by nutrition and treatment with growth hormone in sheep.
Tissue and plasma levels of insulin-like growth factor-I (IGF-I), and relative levels of liver IGF-I RNA, were measured in 6-month-old ewe lambs which were well fed (n = 10) or starved (n = 10) for 5 days. Half of each nutrition group was given daily (09.00 h) injections of human GH (hGH; 0.15 mg/kg body weight per day). Blood was sampled daily from 09.00 to 12.00 h at 15-min intervals through jugular vein catheters and the lambs were slaughtered 24 h after the fifth injection of hGH. Tissue and plasma IGF-I was extracted using an acid-ethanol-cryo-precipitation technique and estimated by radioimmunoassay. Tissue IGF-I was corrected for retained plasma IGF-I using tissue and blood hemoglobin levels. Liver IGF-I RNA levels were monitored by in-situ hybridization. Plasma IGF-I (nmol/l) was higher in both the fed group and the fed group given GH treatment. Tissue IGF-I from kidneys (nmol/kg) was also higher (P < 0.001) in the fed group. There was no significant difference in IGF-I concentrations in the muscle biceps femoris or liver between fed and starved lambs. Although GH treatment did not increase IGF-I levels in tissues significantly, IGF-I RNA levels in liver were increased (P = 0.02) in both fed and starved animals. The relative liver IGF-I RNA levels positively correlated with their corresponding tissue IGF-I levels in the fed group and the fed group given GH treatment.(ABSTRACT TRUNCATED AT 250 WORDS)
Hua
K M
KM
University of Waikato, Hamilton, New Zealand.
Ord
R
R
Kirk
S
S
Li
Q J
QJ
Hodgkinson
S C
SC
Spencer
G S
GS
Molan
P C
PC
Bass
J J
JJ
D000824:Animal Nutritional Physiological Phenomena; D000818:Animals; D013006:Growth Hormone / Q000494:pharmacology*; D007334:Insulin-Like Growth Factor I / Q000235:genetics / Q000378:metabolism*; D007668:Kidney / Q000378:metabolism; D008099:Liver / Q000378:metabolism; D009132:Muscles / Q000378:metabolism; D012313:RNA / Q000032:analysis; D012756:Sheep / Q000378:metabolism*
D012313:RNA; D007334:Insulin-Like Growth Factor I; D013006:Growth Hormone