AJP - Regulatory, Integrative and Comparative Physiology, Vol 271, Issue 4 926-R935, Copyright © 1996 by American Physiological Society
Whole body autoradiography and microautoradiography in eels after intra-arterial administration of 125I-labeled eel ANP
H. Sakaguchi, H. Suzuki, H. Hagiwara, H. Kaiya, Y. Takei, M. Ito, S. Shibabe and S. Hirose
Department of Biological Sciences, Tokyo Institute of Technology, Yokohama, Japan.
125I-labeled eel atrial natriuretic peptide (ANP) was administered into the
ventral or dorsal aorta of freshwater (FW) and seawater (SW) eels, Anguilla
japonica, and the major target organs were explored by whole body
autoradiography. Localization of the ANP binding in the target organs was
also examined at tissue and cell levels by microautoradiography using
tissue sections. Whole body autoradiography revealed that the specific
label was accumulated predominantly in the gill, with lesser amounts in the
atrium, kidney, liver, and urinary bladder. Autoradiographic grains were
most dense in the secondary lamellae of the gill, particularly on the side
of the efferent filamental artery. Other binding sites in target tissues
were the glomerulus of the kidney, epicardium and endocardium of the
atrium, bile duct/blood vessels of the liver, and interrenal cells of the
head kidney. There was no difference in the distribution and density of
grains between injections into the ventral aorta and dorsal aorta,
although, in the former, injected 125I-labeled eel ANP passes through the
gill before reaching peripheral target tissues. There was a tendency for
downregulation of ANP binding sites in SW eels, especially in the gill.
These results show that specific ANP binding sites are present in organs
that are implicated in osmoregulation and cardiovascular regulation in eels
and further suggest that the number of ANP binding sites varies according
to changes in the environmental salinity.
