Characterization of Stanniocalcin-1 Receptors in the Rainbow Trout

Figure 4

ISLB staining of trunk, muscle, kidney, corpuscle of Stannius, and gill. (A) Dorsoanterior trunk; this sagittal section shows that the highest ISLB staining is over epaxial skeletal muscle (skm), followed by spinal cord (sc), nephron (n), and the outer muscularis layer in swim bladder (sb). Hematopoietic tissue (h) within the kidney (k) exhibits weak binding activity. Other abbreviations; s, stromal adipocytes; vb, vertebral body. (B) Skeletal muscle; at high magnification it is evident that STC-1 binding is present over regularly spaced striations that are reminiscent of Z lines (1.5 μM between the red arrows). The inset in panel (B) is an adjacent section stained by ICC, showing STC-1 protein sited over the same regularly spaced striations. (C) Developing kidney tubule; adjacent sections stained by ISLB (top) or hematoxylin & eosin (bottom) reveal a collecting duct (cd) and a developing kidney tubule (yellow asterisk). ISLB staining is evident over collecting ducts but not developing tubules. (D) Atlantic salmon collecting duct; STC-1 binding sites are evident in both the cytoplasm and nuclei (red arrow in D) of collecting duct cells (cd), in contrast to distal tubule cells where binding is cytoplasmic and not nuclear (red arrow in D1). (E) Atlantic salmon corpuscle of Stannius (CS; left) and adjacent kidney tissue (right); binding is strongest to kidney tubules and weaker over STC-1 cells of CS gland (defined by black arrows). Abbreviations: cd; collecting duct; g, glomerulus. (F), Atlantic salmon corpuscle of Stannius (CS) in panel (E) at higher magnification; ISLB staining is highest in red blood cells (black arrows). Staining is also evident over individual cells comprising the CS lobule (red arrows). (G) Gill filament; binding activity is highest in the cytoplasm of isolated cells on and between the primary lamella (red arrows). Staining was absent over filament cartilage (c) and weak elsewhere. The inset at lower right is a staining control.