GH binding to liver in young and old female rats: relation to somatomedin-C secretion.
Age-related changes in binding of 125I-bovine GH to liver membrane fractions were measured in female Long-Evans rats 2, 6, 12 and 20 months of age. Specific GH binding did not change between 2 and 6 months of age but increased significantly at 12 and 20 months of age. Scatchard analysis showed that the plots were curvilinear and consisted of high- and low-affinity binding sites. The age-related increases in binding sites were mainly due to an increase in number of low-affinity binding sites. Serum somatomedin-C (SM-C) levels in 20-month-old rats were about half those in the 6-month-old rats. Twice daily injections of ovine GH (2 mg/kg body wt) for 7 days depressed liver GH binding and increased serum SM-C levels in 19-month-old female rats, but had no effect on GH binding in 2-month-old female rats. These results suggest that the increase in liver GH binding sites and the decrease in SM-C secretion are associated with our previously reported decrease in GH secretion in old female rats.
Takahashi
S
S
Department of Physiology, Michigan State University, East Lansing 48824-1101.
Meites
J
J
D000375:Aging; D000818:Animals; D005260:Female; D013006:Growth Hormone / Q000378:metabolism*; D007334:Insulin-Like Growth Factor I / Q000378:metabolism*; D008099:Liver / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D011986:Receptors, Somatotropin / Q000378:metabolism; D013002:Somatomedins / Q000378:metabolism*
D011986:Receptors, Somatotropin; D013002:Somatomedins; D007334:Insulin-Like Growth Factor I; D013006:Growth Hormone