Somatostatin receptors in wildtype and somatostatin deficient mice and their involvement in nitric oxide physiology in the retina.
The present study investigated the localization and density of somatostatin (SRIF) receptor subtypes (sst(1-5)) and SRIF-nitric oxide (NO()) interactions in the retina of wildtype [WT, (+/+)] and somatostatin deficient mice [SRIF (-/-)]. Immunohistochemistry and radioligand binding studies with subsequent autoradiography were performed. Monoclonal antibodies [SRIF, protein kinase C (rod bipolar cells marker), microtubule associated protein 1A (ganglion cell marker)] and polyclonal antibodies (anti-sst(1), sst(2A), sst(4) receptor) were applied to 10-14 microm sections of retinas fixed in paraformaldehyde. NADPH-diaphorase reactivity was assessed histochemically. [(125)I]LTT SRIF-28 alone or in the presence of MK678 (sst(2) agonist) and [(125)I]Tyr(3)-octreotide were employed to quantify sst(1-5), sst(1/4)and sst(2/5) receptor densities, respectively. sst(1), sst(2A), and sst(4) receptor immunoreactivities were observed in processes of the inner plexiform layer (IPL), rod bipolar, and in ganglion cells and processes, respectively, in WT and SRIF (-/-) mice. Specific [(125)I]LTT SRIF-28 and [(125)I]Tyr(3)-octreotide binding was increased significantly in SRIF (-/-) mice. NADPH-diaphorase staining was localized in photoreceptors and amacrine cells, but not rod bipolar and ganglion cells. Also, NADPH-diaphorase staining was not colocalized with sst(1), sst(2A) or sst(4) receptor immunoreactivity. These results demonstrate an upregulation of SRIF receptors in mice lacking SRIF, but no evident SRIF-NO(*) interaction was observed in the mouse retina.
Mastrodimou
N
N
University of Crete, Faculty of Medicine, Department of Basic Sciences, Laboratory of Pharmacology, Heraklion, Crete 71110, Greece.
Vasilaki
A
A
Papadioti
A
A
Low
M J
MJ
Hoyer
D
D
Thermos
K
K
D000818:Animals; D001345:Autoradiography; D005260:Female; D007150:Immunohistochemistry; D007457:Iodine Radioisotopes; D008297:Male; D008565:Membrane Proteins / Q000235:genetics; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009252:NADPH Dehydrogenase / Q000378:metabolism; D009569:Nitric Oxide / Q000502:physiology*; D015282:Octreotide / Q000378:metabolism; D020419:Photoreceptor Cells, Vertebrate / Q000502:physiology; D011869:Radioligand Assay; D017481:Receptors, Somatostatin / Q000187:drug effects* / Q000235:genetics; D012160:Retina / Q000166:cytology / Q000378:metabolism / Q000502:physiology*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013004:Somatostatin / Q000235:genetics* / Q000502:physiology*
D007457:Iodine Radioisotopes; D008565:Membrane Proteins; D017481:Receptors, Somatostatin; C106140:somatostatin receptor sst2A; C098681:somatostatin receptor subtype-4; C101130:somatostatin receptor type 1; D009569:Nitric Oxide; D013004:Somatostatin; D009252:NADPH Dehydrogenase; D015282:Octreotide