Distribution of phosphatic metabolites in the crystalline lens

The phosphatic metabolite content of specific anatomic regions within the crystalline lens was determined by phosphorus-31 nuclear magnetic resonance analyses performed on tissue perchloric acid (PCA) extracts. Anatomically distinct zones each were dissected from five sets of 10 porcine lenses, isolated, and frozen in liquid N2. Separate pooled-tissue PCA extracts were prepared for each set of lens tissue corresponding to the following anatomic regions: capsule with attached epithelium, cortex, and nucleus. Randomly selected tissues were evaluated by light microscopy to determine the accuracy of the described dissection technique. Thirty-four phosphorus-containing metabolites were detected and quantitated by P-31 NMR from each of the three zones studied. Included among the phosphatic metabolites of these lens tissues were 18 chemically unidentified compounds. Significant regional differences in the metabolite distribution pattern were detected. The levels of ATP in the capsule + epithelium and in the cortex were 2.2-fold and 3.2-fold higher, respectively, than in the nucleus. In contrast, the Pi content was 2.3-fold greater in the capsule + epithelium and nucleus than in the cortex. End products of phospholipid metabolism (eg, glycerol 3-phosphocholine) also varied according to the anatomic region, with the highest content found in the nucleus. The prominent unidentified lens metabolite at 6 delta was highest in the nucleus, 35% lower in the cortex, and quite low in the capsule + epithelium. When individual P-31 NMR spectral profiles from each zone were summed according to normalized weighting factors, which reflected the relative phosphorus concentration of each region, a spectral profile of the lens was generated that was essentially indistinguishable from that of the whole (undissected) lens.(ABSTRACT TRUNCATED AT 250 WORDS)