title: Response of uroporphyrinogen decarboxylase to the hematopoietic demands of the spleen.
abstract: Uroporphyrinogen (urogen) decarboxylase was studied in rat spleen before and after stimulation of splenic hematopoietic cell synthesis with phenylhydrazine (PHZ). Urogen decarboxylase activity was increased over 2-fold following PHZ treatment concomitantly with a comparable increase in spleen weight. The increase in enzyme activity could not be attributed to a direct effect of PHZ on endogenous urogen decarboxylase nor to production of a specific activator of the enzyme in spleen cells. Moreover, the increase in urogen decarboxylase activity following PHZ administration was completely prevented by concomitant treatment with cycloheximide. These findings suggest that urogen decarboxylase activity in spleen represents endogenous porphyrin synthesizing capacity of that tissue, rather than that of sequestered erythrocytes undergoing destruction in that organ. Additionally, they suggest that the capacity for porphyrin synthesis in the spleen is highly responsive to chemically-induced demands for hematopoietic activity.
mesh_terms: D000818:Animals; D002262:Carboxy-Lyases / Q000378:metabolism*; D006413:Hematopoietic System / Q000187:drug effects / Q000378:metabolism*; D006358:Hot Temperature; D008297:Male; D008627:Mercuric Chloride / Q000633:toxicity; D010659:Phenylhydrazines; D014176:Protein Biosynthesis; D051381:Rats; D011919:Rats, Inbred Strains; D013154:Spleen / Q000201:enzymology*; D014575:Uroporphyrinogen Decarboxylase / Q000378:metabolism*
chemical_list: D010659:Phenylhydrazines; C030299:phenylhydrazine; D008627:Mercuric Chloride; D002262:Carboxy-Lyases; D014575:Uroporphyrinogen Decarboxylase