Carrier-enhanced human growth hormone absorption across isolated rabbit intestinal tissue.

Small molecular weight alpha acid derivatives are able to enhance the intestinal absorption of human growth hormone through isolated rabbit intestinal tissue. The enhancement is not through the usual tissue modification associated with traditional penetration enhancers nor is it through an active transport process. Rather these small molecules associate with human growth hormone in solution to make it more transportable through intestinal tissue. It is shown that the enhancer has specificity for a particular protein and the enhancer and human growth hormone must be in solution together to be effective, i.e. pretreating the tissue with enhancer and then adding the protein does not increase tissue permeability. Moreover, the enhancer does not increase the permeability of mannitol or progesterone, thus providing additional evidence of specificity and establishing that these agents are not classical penetration enhancers.