NATURE AND DISTRIBUTION OF GONADOTROPIN-RELEASING-HORMONE (GNRH) IN THE BRAIN, AND GNRH AND GNRH BINDING-ACTIVITY IN SERUM OF THE SPOTTED DOGFISH SCYLIORHINUS-CANICULA

The distribution of different molecular forms of gonadotropin-releasin g hormone (GnRH) in the brain and serum of the spotted dogfish, Scylio rhinus canicula, was investigated by an indirect immunofluorescence me thod, using antisera against salmon (s-), chicken-II (cII-) and mammal ian (m-) GnRHs, and by reverse-phase high-performance liquid chromatog raphy (RP-HPLC) coupled with radioimmunoassays. Five GnRH molecular fo rms were demonstrated on the basis of the retention time in the RP-HPL C system. The characteristics of four of these GnRH peptides are consi stent with those of m-, cII-, dogfish (df-), and sGnRH. The fifth form appears to be novel. Immunoreactive sGnRH structures were confined to the diencephalon; whereas cIIGnRH and mGnRH were found in the telence phalon and diencephalon. cIIGnRH- and dfGnRH-like molecules were detec ted in the serum. Moreover, a specific, low-affinity GnRH binding prot ein (GnRH-BP) was found in the serum of the spotted dogfish. The bindi ng of [I-125]sGnRHA to the serum GnRH-BP was dependent on incubation t ime, equilibrium being reached within 1 hr at 4 degrees; binding was r apid and completely reversible. Scatchard analysis yielded a linear pl ot with a K-d of 7.9 x 10(-7) M. The presence of a GnRH-BP in spotted dogfish serum suggests a probable action of GnRH via the general circu lation. (C) 1995 Academic Press, Inc.