The effect of cyclic adenosine 3',5' monophosphate, methyl xanthines and nicotinic acid on plasma nonesterified fatty acids in sheep.

The intravenous injection of 3', 5' AMP, 10 mg/kg, caused an immediate rise in blood glucose in normal sheep. In sheep where liver glycogen was depleted by pretreatment with 100 mg/kg of nicotinic acid, the blood glucose response was greatly reduced. The glycogenolytic effect of 3', 5' AMP was thus easily demonstrated. The injection of 3', 5' AMP was followed by an immediate rise in NEFA, which was most pronounced in the pretreated animals. After the initial increase there was a fall in NEFA in both the normal and the pretreated animals. The role of hyperglycemia for the NEFA response to exogenous 3', 5' AMP was discussed. It seemed possible that hyperglycemia may modify the initial increase in NEFA. The later fall in NEFA was discussed as a complex response, which may be the result of the action of several hormones, which may be released by 3', 5' AMP injection. Nicotinic acid and pyridyl-3-acetic acid showed a potent antilipolytic activity. Nicotinic acid caused a rebound elevation of NEFA. No rebound was observed after pyridyl-3-acetic acid. Pyridyl-3-acetic acid, however, did not change NEFA when administered orally. Pyridyl-2-acetic acid had no antilipolytic effect. Of the methyl xanthines caffeine and theophylline showed about the same lipolytic activity. Theobromine was quite ineffective.