Demonstration of 20K Growth Hormone in Human Plasma by Gel Electrophoretic-Immunostaining-Autoradiographic Assay (GEISAA)

Summary

A variant of human growth hormone (hGH), in which 15 amino acids are missing (commonly referred to as 20K-hGH in contrast to the traditional form which is referred to as 22K-hGH), is known to exist in human pituitary glands. However, lack of a method to measure it in blood has hindered investigations of its physiopathology. We have applied a newly-developed technique called GEISAA for its detection in small volumes of human plasma. The method is based upon the lower M_r of the variant and its ability to partially crossreact with existing antibodies for 22K-hGH. It consists of retrieval of the substance from plasma by immunoprecipitation, separation from 22K-hGH by NaDodSO₄-polyacrylamide gel electrophoresis, transfer onto nitrocellulose paper by electroblotting and visualization by immunostaining and autoradiography. It revealed the 20K-hGH in plasma of some normal individuals and in that of an acromegalic patient. Furthermore, plasma concentration of the variant rose in conjunction with 22K-hGH following exercise, a natural stimulus for GH release. These results show that the 20K-hGH circulates under normal conditions and it is measurable by GEISAA using existing antibodies.

Key-Words

Human Growth Hormone Variant - Prolactin - Immunostaining - Gel Electrophoresis - Autoradiography - Exercise - Acromegaly