ISSN:
1573-5168
Keywords:
catfish
;
pituitary
;
GnRH
;
receptor
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
Notes:
Abstract Receptors for gonadotropin-releasing hormone (GnRH) were characterized using a radioligand prepared from a superactive analog of salmon GnRH (sGnRH), D-Arg6-Pro9-sGnRH-NEt (sGnRHa). Binding of125I-sGnRHa to catfish pituitary membrane fractions reached equilibrium after 2 h incubation at 4°C. Displacement experiments with several GnRH analogs as well as other peptides, demonstrated the specificity of125I-sGnRHa binding. Specific binding was enhanced in the presence of the cation chelator ethylene bis (oxyethylenenitrilo) tetra-acetic acid (EGTA), indicating an inhibitory effect of cations on GnRH-receptor binding. The binding of125I-sGnRHa to pituitary membranes was found to be saturable at radioligand concentrations of 5 nM and above. A Scatchard analysis of the saturation data suggested the presence of a single class of high-affinity binding sites (Ka=0.901±0.06×109M−1, Bmax=1678±150 fmol/mg protein). A comparative study on125I-sGnRHa binding to pituitary membrane fractions of male and female catfish, indicated that there were no differences in binding affinity and binding capacity between both sexes. The results demonstrate the presence of specific, saturable GnRH receptors in the African catfish pituitary.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF01875646
