Fig. 10. SPARC-null lenses exhibit increased penetration of dye and radioactive tracer. (A) A pair of intact lenses [1 month old, SPARC^+/+ versus SPARC-null (^-/-)] was immersed in trypan blue dye for 20 minutes, as described in the Materials and Methods. Lens capsules with attached epithelium were removed, and decapsulized lenses were immediately photographed. The penetration of the blue dye was increased in the ^-/- lens (equator and peripheral cortex, arrowheads), relative to the ^+/+ lens. Arrows indicate the nucleus of each lens. Bar, 460 µm. (B) Quantitative analysis of dye penetrating into the lens fiber cells and of dye absorbed in the lens capsules with attached epithelial cells. Control (PBS) absorbance was less than 0.005 nm. The amount of dye bound within the capsules of the ^-/- lenses was 1.46 times the value of that bound within the ^+/+ lenses. The dye content measured in decapsulized lenses was 1.38 times the value of ^+/+ lenses. A representative experiment with six lenses for each group (1 month old) is shown. (C,D) Quantitative analysis of [³H]-thymidine tracer penetration into the capsules (with epithelium attached) and lenses in 1-month-old (C) and 3-month-old mice (D). The [³H]-thymidine CPM within the capsules of the ^-/- lenses were 2.5 times (1 month old) and 27 times (3 month old) the values of the corresponding ^+/+ lens capsules. The [³H]-thymidine CPM in ^-/- decapsulized lenses were 1.34 times (1 month old) and 3.35 times (3 month old) the values of the corresponding ^+/+ lenses. Bars in C and D are identified as shown in B. CPM, counts per minute; White bar, control; pink bar and green bar, ^+/+ and ^-/- capsules with attached lens epithelial cells, respectively; purple bar and light blue bar, ^+/+ and ^-/- decapsulized lenses, respectively. Data are the means±s.d.