Increase in 'alkaline' ribonuclease of rat kidney cortex after lysozyme and egg-white administration

Alkaline ribonuclease activity increase in rat kidney cortex and liver after trypan blue and other azo dyes administration

Acid azo dyes, most of them naphtholdisulfonic acid derivatives, were given intraperitoneally to rats and their effect on "alkaline" ribonuclease activity was studied in total homogenates of kidney cortex and liver. Acid treatment was used to release bound enzyme activity. Several of the dyes, including trypan blue, increased RNase activity in both organs 3 days after administration of single doses, while others, like Evans blue, were inactive. Activity was apparently bound to the sulfonic substitution in the 3, 6 positions in the naphthalene rings, substitutions in the benzidine rings being not critical. All of the active and most of the inactive compounds were taken up by tubule cells of kidney cortex and by reticular and parenchymal cells of liver. While the effect on both liver and kidney was obtained 1 day after trypan blue administration, RNase remained increased for only about 3 days in the first organ, and for at least a month in the second. However, repeated trypan blue doses increased liver enzyme activity for at least 9 days. Serum RNase activity was decreased after trypan blue administration. Ethionine administration together with trypan blue markedly blocked the effect of the dye on liver RNase activity; simultaneously given methionine partially reversed the action of the antimetabolite. This suggests that de novo synthesis of RNase is induced in liver by trypan blue. The action of ethionine on the kidney RNase response to trypan blue was less marked although significant; in view of the possible kidney uptake of the plasma enzyme, interpretation of this finding must be postponed. Results are discussed with reference to the mechanism of the structural specificity of the compounds used, cytological localization of the dyes and their mechanism of action on liver and kidney RNase.

Hyaline droplet accumulation in rodent kidney proximal tubules: an association with histiocytic sarcoma

Since recognition during the last decade that certain renal carcinogens can initially cause an accumulation of hyaline (protein) droplets in proximal tubules of male rats, it has become appropriate to establish whether this phenomenon of protein overload can also occur in rodent kidneys unrelated to chemical treatment. Kidney tissue from a number of selected rodent studies held in the National Toxicology Program (NTP) or Food and Drug Administration (FDA) archives were evaluated for hyaline droplet accumulation in proximal tubules. The survey concentrated on rats and mice of both sexes bearing hematopoietic tumors, as our preliminary observations had suggested this direction of study. The tissues of 101 Sprague-Dawley, 25 Osborne-Mendel, and 70 Fischer 344 rats and 96 B6C3F1 mice were examined. These animals provided an assortment of tumors including histiocytic sarcoma, lymphocytic lymphoma, mononuclear cell leukemia, and sarcoma. Hyaline droplet accumulation, primarily involving the P2 segment of proximal tubules, was diagnosed in 96% of rats with histiocytic sarcoma (74/77 cases in Sprague-Dawley, 17/18 in Osborne-Mendels, 7/7 in Fischers) and in 55% of B6C3F1 mice with histiocytic sarcoma (18/33 cases). There appeared to be a qualitative correlation between hyaline droplet accumulation and degree of tumor burden. Thus, in cases negative for hyaline droplets, the tumor was often confined to a single location, while increasing involvement of proximal segments beyond P2 occurred with more extensive multi-organ dissemination of the tumor. By immunohistochemistry on 11 cases of rat and 8 cases of mouse histiocytic sarcoma, the protein in hyaline droplets was identified as lysozyme, a known major secretory product of monocytes and macrophages. The hyaline droplets were negative for alpha 1-antitrypsin, alpha 2u-globulin, rat or mouse immunoglobulin, and albumin. More sparsely scattered droplets and granules present in proximal tubules of Fischer rats with mononuclear cell leukemia were negative for lysozyme but positive for either iron or lipofuscin pigment. The study establishes a clear association between renal tubule hyaline droplet and lysozyme accumulation in rats and mice with histiocytic sarcoma. Hyaline droplets secondary to neoplasia should be distinguished from chemically-induced hyaline droplet nephropathy in the male rat involving alpha 2u-globulin.

Metal-ion effects on proteolysis and stability in secondary lysosomes of mouse kidney

In previous studies, in vitro digestion of [1 2 5-I] ribonuclease by lysosomes of mouse kidney was limited because breakdown, which was rapid at first, slowed markedly so that most of the labeled protein escaped degradation. We now describe incubation conditions which allow digestion to proceed until approximately 70% of the exogenous protein label is released in acid-soluble form, after 30-45 min at 37 degrees C. Such activity is seen with either the addition of EDTA or incubation of concentrated cell particle suspensions. EDTA is effective in low concentrations and shows the same stimulation of digestion over a range of approximately 10-minus 6--10-minus 3 M. Other chelating agents have similar effects; dipyridyl and hydroxquinoline are as effective as EDTA, o-phenanthroline and diethyldithiocarbamate are slightly less effective. When the incubation medium had been treated with a chelating resin, Chelex 100, dilute suspensions of lysosomes were as active as those in EDTA. These results lead to the conclusion that metal ions, present as contaminants in very small concentrations, inhibit the activity of mouse kidney lysosomes. The effect of the metal ions is to diminish lysosomal stability, leading to release of intact labeled ribonuclease in non-sedimentable form. Interaction between lysosomes and metal, leading to inhibition of digestion upon heating, occurs at low temperature, but breakdown requires incubation at 37 degrees C and may be autolytic. In contrast to chelators, mercaptoethanol is without marked effect on stability; the stimulation in digestion rate caused by this agent is due either to a direct effect on the lysosomal enzymes or to a non-destructive influence on the lysosomal structure.