Luteinizing hormone secretion from the quail pituitary in vitro

An enzymatically dispersed pituitary preparation from Japanese quail (Coturnix coturnix) was used to study the dynamics of gonadotropin release. After an 18-h incubation, the cells were challenged with different luteinizing hormone-releasing hormones (LHRH) for 90 min. Using pituitary cells from mature males, mammalian and chicken LHRH I (Gln8-LHRH) had approximately equal luteinizing hormone (LH)-releasing activity whereas chicken LHRH II (His5, Trp7, Tyr8-LHRH) was 8-9 times more potent. The LHRH agonist (Trp6, Pro9-NEt-LHRH) had 15 times greater potency than chicken LHRH I. Pre-incubation with an LHRH antagonist (D-Phe2, D-Trp6-LHRH) significantly suppressed LH release. Acid extracts of median eminence released LH from pituitary cells, extracts from short-day and long-day males had equal activity, while tissue extracts from castrated males had significantly greater LH-releasing activity. Pituitary cells from sexually immature males released LH in response to chicken LHRH I in a similar profile to cells from mature males. These data indicate that the quail LHRH receptor in the male recognizes several different molecular species of LHRH and the response to LHRH is comparable between short- and long-day males. Pituitary cells from ovulating females were variably sensitive to LHRH peptides, possibly due to changes in pituitary sensitivity during the ovulatory cycle. Pituitary cells from immature females did not release LH in response to chicken LHRH I. However, pituitary cells from immature females photostimulated for 1 wk displayed a response to chicken LHRH I and II similar to that of pituitary cells from males.(ABSTRACT TRUNCATED AT 250 WORDS)