Effect of high level section of the spinal cord on the cyclic AMP system in rat liver

Catecholamine concentration in rat liver after high level transection of the spinal cord

The high level transection of the spinal cord (C-7) provokes a sustained increase of rat liver catecholamines: biphasic increase in norepinephrine level 1 hour and 24 hour after the operation and 7-fold increase of dopamine content 4 hour after the chordotomy. In contrast to cervical transection, sham operation causes only an initial catecholamine increase, the maximum being at the first hour after the surgery. Our experimental data indicate a possible participation of cervical spinal pathways in regulation of liver catecholamine content. It is also shown that bilateral adrenalectomy augments liver norepinephrine concentration in spinal rats as compared to the non-adrenalectomized ones. The results presented here indicate that cervical chordotomy affects the functioning of the sympatho-adrenal system, thus provoking specific changes in liver catecholamine content. The potential effect of such changes on a liver metabolic system (tyrosine aminotransferase induction) is discussed.

Variations of cyclic AMP and cyclic GMP contents of the liver and of brown and white adipose tissues of the rat during the first week of cold exposure

The variation in the amounts of cyclic AMP and cyclic GMP were studied in white and brown adipose tissues and in the liver of rats during the first week of cold exposure (5 degrees C). In white fat, only a small increase in cAMP was observed on the first day. In brown fat, parallel decreases in cAMP and cGMP contents were induced which might be related to a large mobilization of tissue fatty acids. In the liver, cold exposure barely affected the cAMP content but the level of cGMP was markedly increased. These results are discussed with regard to the respective role of these different tissues in cold-induced energetic substrate mobilization.