Development of a technique for measuring insulin-like growth factor-I in swine:application to the study of the IN VIVO and IN VITRO effects of growth hormone in neonatal pigs

The relationship between porcine growth hormone (pGH) and insulin-like growth factor-I (IGF-I) in swine was investigated. IGF-I levels were measured by radioimmunoassay (RIA) with an antisera specific for human IGF-I after ultrafiltration of acidified samples. Ultrafiltration quantitatively separated carrier proteins and IGF-I. Failure to separate these species interfered with the RIA. Using this assay, swine chronically treated with pGH had 2.6-fold higher sera levels of IGF-I than controls, whereas, serum IGF-I from a hypophysectomized animal was only 4% that of normal animals. The ultrafiltration procedure was incorporated into a protocol to measure IGF-I in sera from neonatal swine treated with pGH (5O ug •kg BWt⁻¹•d⁻¹). Treatment of neonatal pigs with pGH for one or two weeks elevated pGH in sera, but did not significantly affect either growth or serum IGF-I concentrations. Preliminary studies were performed to determine if neonatal swine hepatocytes secreted IGF-I in vitro. Results indicated that neonatal hepatocytes synthesized limited quantities of IGF-I that approached the detection limits of the RIA. Furthermore, pGH did not stimulate hepatocyte IGF-I synthesis in vitro or in vivo. Neonatal hepatocytes synthesized a protein species that bound labeled IGF-I and had a molecular weight similar to a carrier protein in swine serum. Estimation of the rate of carrier protein synthesis suggested that IGF-I and carrier proteins are coordinately regulated in isolated neonatal hepatocytes. These results suggest that IGF-I is not inducible in the neonatal pig by GH therapy and that growth in neonatal swine is either maximal or GR-independent.

Name thesis:degree_name

M.S.

Level thesis:degree_level

masters

Discipline thesis:degree_discipline

Biochemistry and Nutrition

Department dc:contributor.department

Biochemistry and Nutrition

Grantor dc:publisher

Virginia Polytechnic Institute and State University

Year dc:date.issued

1986

Author dc:creator

• Scamurra, Ronald W.

Statement dc:rights

• In Copyright

Licence dc:rights.uri

• http://rightsstatements.org/vocab/InC/1.0/

Language dc:language.iso

en_US

Handle dc:identifier.uri

http://hdl.handle.net/10919/91042

OAI identifier oai:identifier

oai:vtechworks.lib.vt.edu:10919/91042