Implantation of MtT-F4
tumor, a mammotropic
tumor that secretes large quantities of
ACTH, GH and
prolactin, into male Fisher rats induced the development of
hyperlipidemia.
Free fatty acid,
triglyceride and
cholesterol levels in the plasma were significantly increased at 31 days after
tumor implantation.
Blood glucose and
glycerol levels remained normal, while
uric acid concentration in the blood was significantly decreased. The concentrations of the serum
lipoproteins were significantly increased, while, only small changes in the distribution of the serum
lipids and the composition of the
lipoproteins were observed. Following stimulation of isolated adipose tissue cells with
ACTH, the lipolytic response and the accumulation of
cyclic AMP was higher in cells derived from the rats with the
tumor, although the accumulation of
cyclic GMP was not different from control adipocytes. Further, when the isolated adipose tissue cells were stimulated with
dibutyryl cyclic AMP no difference was observed between the control and
tumor bearing groups.
Clofibrate administered in the diet resulted in a complete elimination of the
tumor effect on serum
triglycerides and to a great extent prevented the rise in serum
cholesterol. The
tumor-induced increase in the concentration of the
high density lipoproteins was not affected, but the elevation of the d less than 1.063
lipoproteins was not affected, but the elevation of the d less than 1.063
lipoproteins was partially reversed. The increased lipolytic response and accumulation of
cyclic AMP following stimulation by
ACTH was not altered in adipocytes derived from
tumor bearing rats. However,
clofibrate treatment resulted in a significantly greater accumulation of
cyclic GMP in fat cells stimulated with
ACTH from both control and
tumor bearing rats.
Clofibrate in the diet did not alter the levels of GH or
prolactin or serum
lipids in the control rats nor were the elevated
hormone levels of the
tumor bearing rats changed.