RECOMBINANT RAT FOLLICLE-STIMULATING-HORMONE - PRODUCTION BY CHINESE-HAMSTER OVARY CELLS, PURIFICATION AND FUNCTIONAL-CHARACTERIZATION

In order to obtain homologous follicle-stimulating hormone (FSH) for i n vivo and in vitro studies in the rat, rat recombinant (rec) FSH was produced in Chinese Hamster Ovary (CHO) cells. The synthesized rat rec FSH was purified and subjected to physico-chemical and biological char acterization, including a comparison with two rat pituitary (pit) and reference preparations (NIDDK-rFSH I-8 and NIDDK-rFSH-RP2) as well as with human recFSH (Org 32489). The molecular masses of rat recFSH and human recFSH were determined by SDS-polyacrylamide (SDS-PAGE) and were found to be similar, about 40 kD. The pI distribution of rat recFSH i s similar to rat pitFSH, and slightly more acidic than human recFSH (3 .6-5.6 vs 3.9-5.5, respectively) as determined by isoelectric focussin g in immobilized pH gradients. Rat recFSH displayed dose-response curv es parallel and in the same dose range as the rat pitFSH in receptor b inding and in vitro bioassays. However, the in vivo activities of rat recFSH and rat pitFSH were 8824 and 3051 IU/mg, respectively, determin ed by the Steelman Pohley assay. Rat (pit and rec) and human FSH are v ery different. Human recFSH bound to both calf testicular membranes an d CHO cells expressing the human FSH receptor (CHO hFSH-R) with about 10-fold higher affinity (Ka) than pituitary and recombinant rat FSH. I n in vitro bioassays with immature rat Sertoli cells and CHO hFSH-R ce lls human recFSH was also about 10-fold more potent than the rat FSH p reparations. In the in vitro bioassays with immature rat granulosa cel ls the difference was about 5-10-fold. These studies indicate that the receptor binding and in vitro activities of rat pitFSH and rat recFSH are similar. The differences in in vivo activity are probably due to the differences in glycosylation. The biological behaviour of rat FSH (pit and rec) is different from that of human FSH. Therefore, if the r at is used as a model for physiology of gonadotropic action, the resul ts may be greatly influenced by the type (species) of hormone preparat ion used. The availability of homologous hormone preparations is there fore crucial. (C) 1997 Elsevier Science Ireland Ltd.