Evidence of facilitory effect of growth hormone on tissue vitamin A uptake in rats
Ahluwalia, G.S.; Kaul, L.; Ahluwalia, B.S.
Journal of Nutrition 110(6): 1185-1193
1980
ISSN/ISBN: 0022-3166 PMID: 7189776 Document Number: 160264
The effect was studied of somatotropin (GH) on liver vitamin A release and uptake at the tissue level. Labelled vitamin A (retinol) was injected into hypophysectomized (hypox) rats, and plasma radioactivity was monitored at intervals for up to 6 h and at 24 h after injection. Controls, intact sham-operated, received similar treatment. The results showed that the radioactivity reached its maximum values in both groups between the 3rd and 4th h after injection and declined thereafter at different rates in each group. At 24 h after injection plasma radioactivity in the intact rats was less than 10% of its maximum value; in the hypox rats for the same time period it remained at 80 to 90% of its maximum value. A single injection of GH at the third hour after injection in the hypox rats decreased significantly plasma radioactivity whereas radioactivity in the testes and kidneys and in urine collected for the 24 h increased significantly. Hypophysectomy had no effect on vitamin A absorption and liver vitamin A release to the blood; it had no significant effect on plasma and tissue retinol-binding protein and its binding capacity to retinol. It is concluded that a facilitory effect of GH at the tissue level may be an important factor in vitamin A metabolism.