Purification of gonadotropic hormone from the pituitary of the African catfish, Clarias gariepinus (Burchell), and the development of a homologous radioimmunoassay.

Glycoprotein gonadotropic hormone (GTH) was purified from 2000 pituitaries of male and female African catfish, Clarias gariepinus. The first step was chromatography on concanavalin A-Sepharose followed by filtration on Ultrogel Aca 54, chromatography on DEAE-cellulose, and filtration on Ultrogel Aca 54, respectively. Finally, the purified fractions were analyzed by polyacrylamide gel electrophoresis. The gonadotropic activity in the different fractions was characterized using two tests: the radioimmunoassay for carp gonadotropin-beta subunit was used to quantify the immunoreactive GTH and a cAMP accumulation test was applied to measure the GTH biological activity. The purified glycoprotein GTH was used to raise antibodies and to develop a radioimmunoassay. This resulted in an assay with a variation between assays of approximately 4%, a precision of 4-8%, and an accuracy of 4-8%. GTH levels can be measured over a range of 0.8 to 12.5 ng/ml.