Stimulation of luteinizing hormone release from chicken pituitary cells by analogues of luteinizing hormone-releasing hormone

The luteinizing hormone (LH) releasing activities of luteinizing hormone-releasing hormone (LH-RH) and four related analogues were compared using isolated chicken anterior pituitary cells. The analogues, des-Gly 10-LH-RH and Phe 5-LH-RH, exhibited a greater potency than LH-RH (150 and 237%, respectively), whereas LH-RH(OH) was much less active (1.1%). The potency of Phe 5-LH-RH was reduced to 0.9% by the insertion of a tyrosine molecule at position 11, indicating that chain length is a significant feature of the biological activity of the molecule. des-Gly 10-LH-RH and Phe 5-LH-RH were more active in the present system, than is indicated by available information for the rat.