Decreased response to cAMP in the glucose and glycogen catabolism in perfused livers of Walker-256 tumor-bearing rats.
The hepatic response to cyclic adenosine monophosphate (cAMP) and N6-monobutyryl-cAMP (N6-MB-cAMP) in the glucose and glycogen catabolism and hepatic glycogen levels were evaluated in Walker-256 tumor-bearing rats, on days 5 (WK5), 8 (WK8), and 11 (WK11) after the implantation of tumor. Rats without tumor fed ad libitum (fed control rats) or that received the same daily amount of food ingested by anorexics tumor-bearing rats (pair-fed control rats) or 24 h fasted (fasted control rats) were used as controls. Glucose and glycogen catabolism were measured in perfused liver. Hepatic glycogen levels were lower (p < 0.05) in WK5, WK8, and WK11 rats in comparison with fed control rats, but not in relation to the pair-fed control rats. However, the stimulatory effect of cAMP (3 and 9 μM) in the glycogen catabolism was lower (p < 0.05), respectively, in WK5 and WK8 rats compared to the pair-fed and fed control rats. Accordingly, the suppressive effect of cAMP (6 μM) in the glucose catabolism, under condition of depletion of hepatic glycogen (24 h fast), was lower (p < 0.05) in WK5 and WK11 rats than in fasted control rats. Similarly, the suppressive effect of N6-MB-cAMP (1 μM), a synthetic analogue of cAMP that it is not degraded by phosphodiesterase 3B (PDE3B), in the glucose catabolism was lower (p < 0.05) in WK5 rats compared to fasted control rats. In conclusion, livers of Walker-256 tumor-bearing rats showed lower response to cAMP in the glucose and glycogen catabolism in various stages of tumor development (days 5, 8 and 11), which was probably not due to the lower hepatic glycogen levels nor due to the increased activity of PDE3B.
Department of Physiological Sciences, State University of Londrina, Londrina, PR 86051-990, Brazil.
Hely
H
de Morais
Priscila
P
Cassola
Carolina Campos Lima
CC
Moreira
Suéllen Kathiane Fernandes Vilas
SK
Bôas
Glaucia Regina
GR
Borba-Murad
Roberto Barbosa
RB
Bazotte
Helenir Medri
HM
de Souza
D000818:Animals; D002279:Carcinoma 256, Walker / Q000378:metabolism* / Q000473:pathology; D000242:Cyclic AMP / Q000378:metabolism*; D054684:Cyclic Nucleotide Phosphodiesterases, Type 3 / Q000378:metabolism; D005947:Glucose / Q000378:metabolism*; D006003:Glycogen / Q000378:metabolism* / Q000494:pharmacology*; D008099:Liver / Q000378:metabolism* / Q000473:pathology; D008297:Male; D009363:Neoplasm Proteins / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D013997:Time Factors
D009363:Neoplasm Proteins; D006003:Glycogen; D000242:Cyclic AMP; D054684:Cyclic Nucleotide Phosphodiesterases, Type 3; C517294:Pde3b protein, rat; D005947:Glucose