Short-term trials with a triazin derivative and a peptide aldehyde were carried out to investigate the in-vivo administration of proteinase inhibitors in rats for improving the N balance of the animals. The results of N balances suggest that the peptide aldehyde may be regarded as a promising substance that may be used to increase the rate of utilization of the absorbed N in the intermediary metabolism. The short-term use of both active compounds did not affect the true N digestibility. The two compounds did not influence the concentration of free amino acids in the liver and muscle tissue under the experimental feeding conditions used. Similarly, tests of the biological half-life of proteins taken from the small and large intestine did not reveal any changes due to the presence of the inhibitors. Animals receiving a protein-free diet exhibited longer half-life periods for proteins from the small and large intestine compared with animals of the other groups. A protein-free nutrition of the animals caused a general increase in the levels of free non-essential amino acids in the liver. This was accompanied by a simultaneous decrease in essential amino acids. The same type of nutrition led to a general decline in the concentration of free amino acids in muscular tissue, particularly of the essential amino acids. High-protein nutrition led especially to an increase in the concentration of branched-chain amino acids in both types of tissues investigated.

Murine class III receptors for IgG (mFc gamma RIII) are composed of an IgG-binding alpha chain associated with a gamma subunit dimer. These receptors have been shown to trigger the release of serotonin and tumor necrosis factor-alpha [Daëron, M., Latour, S., Hückel, C., Bonnerot, C. & Fridman, W. H. (1992) Immunobiology 185, 159-174], and are involved in endocytosis and phagocytosis [Daëron, M., Malbec, O., Bonnerot, C., Latour, S., Segal, D. M. & Fridman, W. H. (1994) J. Immunol. 152, 783-792]. Using a transfection model where the cDNA encoding mFc gamma RIII was stably transfected into the rat basophilic leukemia cell line RBL-2H3, we found that the functional efficiency of mFc gamma RIII is correlated with its ability to increase the intracellular Ca2+ concentration and to stimulate inositol phosphate metabolism. The deletion of intracellular sequences of the alpha subunit did not alter the ability of mFc gamma RIII to trigger the Ca2+ and phosphatidylinositol 4,5-bisphosphate [PtdIns(4,5)P2] response. After substitution of the intracellular domain of mFc gamma RIII for that of mFc gamma RIII gamma, but not that of mFc gamma RIII alpha, the chimeric receptor was also able to trigger Ca2+ and PtdIns(4.5)P2 responses. In contrast, all transfected receptors induced protein kinase C translocation. Furthermore, dimerization of the receptor was sufficient for the initiation of this protein kinase C translocation while a further crosslinking was necessary for the induction of the Ca2+ and PtdIns(4,5)P2 responses. Protein kinase C translocation therefore can be dissociated from Ca2+ mobilization, PtdIns(4,5)P2 turnover and mast cell secretory responses induced by murine Fc gamma RIII.

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Murine class I11 receptors for IgG (mFcyRII1) are composed of an IgG-binding a chain associated with a y subunit dimer. These receptors have been shown to trigger the release of serotonin and tumor necrosis factor-a [Daeron, M., Latour, S., Hiickel, C., Bonnerot, C Zmmunol. 152,. Using a transfection model where the cDNA encoding mFcyRIII was stably transfected into the rat basophilic leukemia cell line RBL-2H3, we found that the functional efficiency of mFcyRIII is correlated with its ability to increase the intracellular Ca2+ concentration and to stimulate inositol phosphate metabolism.The deletion of intracellular sequences of the a subunit did not alter the ability of mFcyRII1 to trigger the Ca2+ and phosphatidylinositol 4,5-bisphosphate [PtdIns(4,5)P2] response. After substitution of the intracellular domain of mFcyRII for that of mFcyRIIIy, but not that of mFcyRIIIa, the chimeric receptor was also able to trigger Caz+ and PtdIns(4,5)P2 responses.In contrast, all transfected receptors induced protein kinase C translocation. Furthermore, dimerization of the receptor was sufficient for the initiation of this protein kinase C translocation while a further crosslinking was necessary for the induction of the Ca2+ and PtdIns(4,5)P2 responses.Protein kinase C translocation therefore can be dissociated from Ca2+ mobilization, PtdIns(4,5)P2 turnover and mast cell secretory responses induced by murine FcyRIII.