Differential effects of parenteral nutrition on tumor growth and erythrocyte polyamine levels in the rat

The influence of total parenteral nutrition (TPN) on tumor growth and erythrocyte polyamine levels was evaluated in rats with a transplantable fibrosarcoma or a Ward colon tumor. During the experimental periods the fibrosarcoma grows exponentially when rats are fed chow ad libitum while the colon tumor reaches a plateau of its Gompertzian growth curve. A 12-day regimen of TPN resulted in an increased growth of the colon tumor but not the fibrosarcoma. The erythrocyte putrescine levels of fibrosarcoma-bearing rats and the levels of putrescine, spermidine, and spermine of Ward colon-tumor-bearing rats were significantly increased by TPN compared with similarly treated nontumor-bearing (NTB) rats. When the growth of the fibrosarcoma was slowed by feeding a restricted intake (RI) regimen, a subsequent 6-day regimen of TPN resulted in increased tumor growth. Erythrocyte polyamine levels of fibrosarcoma-bearing, RI-rats were elevated by TPN repletion. There was a consistent, significant, interaction between TPN and tumor presence on the erythrocyte putrescine levels in fibrosarcoma-bearing rats and the levels of all polyamines in Ward colon-tumor-bearing rats. The effects of TPN on tumor growth and erythrocyte polyamine levels of tumor-bearing rats may be dependent on the growth characteristics of the tumor. The data demonstrate that TPN consistently enhanced the tumor contribution to the erythrocyte putrescine pool.