Beta-endorphin and corticotropin immunoreactivity and specific binding in the neuromuscular system of obese-diabetic mice.
Immunoreactivity for two derivatives of pro-opiomelanocortin, beta-endorphin and alpha-melanocortin (or corticotropin), was demonstrated, using a conventional immunoperoxidase method, in some of the intramuscular nerves in muscle sections from obese diabetic (ob/ob) mice and homozygous lean (+/+) mice. The endplate regions were visualized in the sections by staining for acetylcholinesterase reaction product. The proportion of muscle endplates with beta-endorphin-immunoreactive motor nerves was approximately 2.5-fold higher in soleus and extensor digitorum longus muscles and approximately 1.5-fold higher in the diaphragm of the obese (ob/ob) mice compared to the normal lean mice. The proportion of muscle endplates with alpha-melanotropin-immunoreactive motor nerves was between 30 and 53% lower, depending on the muscle type, in the ob/ob mice compared to the lean mice. The muscles of ob/ob and lean mice were investigated for the presence of specific binding sites for [125I]beta-endorphin and for [125I]corticotropin, using autoradiography. Some muscle fibres in soleus, extensor digitorum longus and diaphragm in both the ob/ob and the lean mice exhibited specific binding sites for the radioactive ligands. The binding sites were distributed over the entire surface in these muscle fibres. In the ob/ob mice the number of muscle fibres with specific [125I]beta-endorphin binding sites was six-fold higher in soleus and approximately 10-fold higher in extensor digitorum longus and diaphragm, than in the corresponding muscles of the lean mice. In contrast, the number of muscle fibres with specific [125I]corticotropin binding sites was similar in obese (ob/ob) and lean mice.(ABSTRACT TRUNCATED AT 250 WORDS)
Hughes
S
S
Department of Physiology, Medical School, University of Birmingham, U.K.
Smith
M E
ME
Bailey
C J
CJ
D000324:Adrenocorticotropic Hormone / Q000032:analysis / Q000378:metabolism*; D000818:Animals; D001345:Autoradiography; D001665:Binding Sites; D003920:Diabetes Mellitus / Q000378:metabolism* / Q000473:pathology; D003921:Diabetes Mellitus, Experimental / Q000378:metabolism* / Q000473:pathology; D007124:Immunoenzyme Techniques; D007457:Iodine Radioisotopes; D051379:Mice; D008810:Mice, Inbred C57BL; D008820:Mice, Obese; D009045:Motor Endplate / Q000378:metabolism* / Q000648:ultrastructure; D009132:Muscles / Q000378:metabolism* / Q000473:pathology; D009765:Obesity; D018043:Receptors, Corticotropin; D011957:Receptors, Opioid / Q000032:analysis / Q000378:metabolism*; D011979:Receptors, Pituitary Hormone / Q000032:analysis / Q000378:metabolism*; D012016:Reference Values; D000521:alpha-MSH / Q000032:analysis / Q000378:metabolism; D001615:beta-Endorphin / Q000032:analysis / Q000378:metabolism*
D007457:Iodine Radioisotopes; D018043:Receptors, Corticotropin; D011957:Receptors, Opioid; D011979:Receptors, Pituitary Hormone; D000521:alpha-MSH; D001615:beta-Endorphin; D000324:Adrenocorticotropic Hormone