Tissue Enzyme Changes in Parabiotic Rats With Subcutaneous Lymphoma or Fibrosarcoma 2 3

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Abstract
A solid lymphoma implanted into normal inbred Kx rats and one partner of parabiotic pairs caused appreciable decreases in hepatic ornithine aminotransferase and arginase about a week earlier (4-S days aHer implantation) in single hosts than in parabiotic hosts. By 18–21 days significant decreases in both enzymes were apparent in the host partner also. The hepatic thymidine kinase showed a fivefold elevation in single hosts 4 days aHer implantation; by 14 days its levels were about 200 times above normal and had also risen in the parabiotic hosts (20-fold) and host partners (fourfold). Implantation of fibrosarcoma caused qualitatively similar but generally less pronounced changes in these three enzymes in livers of single hosts, parabiotic hosts, and host partners. The splenic thymidine kinase 14 days aHer implantation was increased from control levels of about 3 U/g to 50.S, 44.8, and 13.5 Ulg in single hosts, parabiotic hosts, and host partners, respectively. At later stages, 17–20 days aHer implantation of the lymphoma, appreciable amounts of thymidine kinase appeared in the plasma: The units of activity per milliliter were 6.2 in single hosts, 0.79 in parabiotic hosts, and 0.55 in host partners (control <0.05). Our observations on the changes in hepatic and splenic enzymes in parabiotic rats suggest that effects of neoplasms on distant host tissues are mediated by humoral factors. The less pronounced responses in parabiotic than in single hosts indicate that the tumor-free partner affords some “protection” against these systemic effects.