Characterization and distribution of prolactin releasing peptide (PrRP) binding sites in the rat - evidence for a novel binding site subtype in cardiac and skeletal muscle
F. Satoh et al., Characterization and distribution of prolactin releasing peptide (PrRP) binding sites in the rat - evidence for a novel binding site subtype in cardiac and skeletal muscle, BR J PHARM, 129(8), 2000, pp. 1787-1793
1 Prolactin releasing peptide (PrRP) was recently purified from bovine hypo
thalamus and binds to the orphan receptor, UHR-1. We examined the distribut
ion and kinetics of I-125-PrRP binding in rat tissues together with molecul
ar characterization by chemical cross-linking and Northern blotting.
2 In this study I-125-PrRP binding showed specificity and rapid association
and dissociation.
3 Specific binding was found in membranes from rat tissues including brain
(hypothalamus, medulla oblongata and cerebellum) pituitary, heart, soleus m
uscle, adipose tissue, kidney, adrenal gland, testis and small intestine. I
n hypothalamus, pituitary, heart and soleus competition analysis indicated
only one class of binding site in each tissue. Binding affinity for PrRP (I
C50) and binding site density (B-max) respectively were 5.2+/-0.9 nM and 67
4+/-97 fmol mg protein(-1) in hypothalamus (n=5), 1.4+/-0.6 nM and 541+/-12
6 fmol mg protein(-1) in pituitary (n=3), 6.6+/-0.7 nM and 628+/-74 fmol mg
protein(-1) in heart (n=4) and 9.8+/-0.9 nM and 677+/-121 fmol mg protein(
-1) in soleus muscle (n=4).
4 Analysis of I-125-PrRP-binding site complexes by chemical cross-linking s
howed a binding site M-r of 69,000 in hypothalamus and 41,000 in heart and
soleus.
5 Northern analysis of polyA(+) RNA from hypothalamus showed a 4.2 kb band
as expected for UHR-1, but heart and soleus showed a 4.8 kb band.
6 Taken together these results indicate that there may be different subtype
s of PrRP binding sites in rat tissues which may differ from UHR-1.