Peptides co-released with luteinizing hormone by perifused pituitary cell aggregates.
The proteins co-released with gonadotropins were analyzed using perifusion of pituitary cell aggregates from 14-day-old female rats, after a pre-labeling period with [35S]methionine. Radioimmunoassays of hormones and electrophoretic analysis were performed on each 4 min effluent. Gonadotropin-releasing hormone (GnRH) pulses increased significantly (P less than 0.01) the release of several proteins (Mr range from 140,000 to 28,000). The main stimulation appeared for -1, a 87 kDa species, previously characterized as gonadotrope polypeptide 87 (GP87) in monolayer cultures and identified as a secretogranin II (SgII) form; -2, a second species of 80 kDa designated as B2. Secretory patterns of radiolabeled GP87 and B2 paralleled the luteinizing hormone (LH) ones. The release of these species was -1, GnRH dose dependent; -2, monophasic for short pulses but complex when the duration of GnRH pulses increased to 16 min, suggesting different pools of GP87 and B2 as for LH; -3, induced by thyrotropin-releasing hormone (TRH). A slight output was also elicited by corticotropin-releasing factor (CRF) and growth hormone-releasing hormone (GHRH), but this release was partly impaired in the presence of a potent anti-GnRH ([Ac-D-(2)-NAL1,pF-D-Phe2,D-Trp3,D-Arg6]-LAF) suggesting a non-specific effect of these two factors. GP87/SgII thus appeared mainly associated with the release of hormonal glycoproteins. In conclusion, perifusion of pituitary cell aggregates allows a precise minute-to-minute kinetic analysis of the various proteins co-released with hormones. The similar timing in output of LH, GP87 and B2 suggests that these three proteins co-exist in the same secretory granules inside gonadotropes.
Sion
B
B
U.A. C.N.R.S. No. 256, Université de Rennes I, France.
Chanat
E
E
Duval
J
J
Thieulant
M L
ML
D000818:Animals; D002864:Chromogranins; D003346:Corticotropin-Releasing Hormone / Q000494:pharmacology; D004591:Electrophoresis, Polyacrylamide Gel; D005260:Female; D007987:Gonadotropin-Releasing Hormone / Q000008:administration & dosage / Q000494:pharmacology; D013007:Growth Hormone-Releasing Hormone / Q000494:pharmacology; D007986:Luteinizing Hormone / Q000378:metabolism*; D010455:Peptides / Q000378:metabolism*; D010902:Pituitary Gland / Q000187:drug effects / Q000378:metabolism*; D011506:Proteins / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D013973:Thyrotropin-Releasing Hormone / Q000494:pharmacology
D002864:Chromogranins; D010455:Peptides; D011506:Proteins; D007987:Gonadotropin-Releasing Hormone; D013973:Thyrotropin-Releasing Hormone; D007986:Luteinizing Hormone; D003346:Corticotropin-Releasing Hormone; D013007:Growth Hormone-Releasing Hormone