Enhanced growth by ectopic expression of growth hormone releasing hormone using an injectable myogenic vector.

Ectopic expression of a truncated growth hormone-releasing hormone (GHRH) from muscle tissues by a myogenic plasmid DNA vector directed by the skeletal alpha-actin promoter, pSK-GHRH, results in growth hormone (GH) secretion. Skeletal muscle-secreted GHRH is biologically active. The application of conditioned media harvested from pSK-GHRH transfected muscle cells to cultured pig primary anterior pituitary cells elicits GH release. A single intramuscular injection of 100 micrograms pSK-GHRH DNA elevates serum GH levels threefold to fourfold for up to 2 weeks, enhancing liver IGF-1 gene expression and increasing body weight approximately 10%.