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Biomedical subjects

J N Fain

Publications and source records attributed to J N Fain.

At least 163 records · Page 9Linked to original sources
PubMed1975

Insulin, prostaglandin E1, PHENYLISOPROPYLADENOSINE AND NICOTINIC ACID AS REGULATORS OF FAT CELL METABOLISM.

Insulin-stimulated glucose oxidation was enhanced by the addition of N6 (phenylisopropyl)adenosine (PIA), prostaglandin E1 (PGE1) or nicotinic acid during a 1-h incubation of small amounts 5-8 mg/ml) of rat fat cells. Basal lipolysis was appreciable if low numbers of fat cells were incubated per ml. Insulin inhibited basal lipolysis at 20 to 50 mugU/ml and abolished lipolysis of 100 mugU/ml was present over a l-h period. However PIA, PGE1 or nicotinic acid potentiated glucose oxidation due to the 100 mugU/ml dose of insulin indicating that these agents are not increasing glucose oxidation solely as a result of an inhibition of lipolysis. PIA, PGE1 and nicotinic acid acted synergistically with insulin in stimulating glucose oxidation and inhibiting lipolysis in the presence of norepinephrine. Insulin was unable to decrease basal cyclic AMP accumulation or the increase in cyclic AMP seen with norepinephrine and theophylline after various time periods (2 to 60 min) but PIA, PGE1 and nicotinic acid were able to inhibit cyclic AMP accumulation at all times tested.

Adipose Tissue↗
PubMed1975

Inhibition of lipolysis and cyclic AMP accumulation in white fat cells by tetracycline.

The effects of tetracycline on the metabolism of isolated rat white fat cells were examined. Tetracycline at a concentration of 0.05 mg/ml inhibited lipolysis due to 0.075 or 0.15 muM norepinephrine, but not that due to adenosine deaminase, theophylline, dibutyryl cyclic AMP or 1.5 muM norepinephrine. Higher concentrations of tetracycline (1 mg/ml) inhibited lipolysis due to all added agents except dibutyryl cyclic AMP. The accumulation of cyclic AMP after 5 minutes incubation with 0.15 muM norepinephrine plus adenosine deaminase was inhibited by 0.05 mg/ml of tetracycline. The large rise in cyclic AMP accumulation at 5 minutes due to 1.5 muM norepinephrine in the presence of 100 muM theophylline was only slightly inhibited by 0.05 or 0.1 mg/ml of tetracycline. Tetracycline at 1 mg/ml did markedly inhibit cyclic AMP accumulation due to all added agents. The stimulation of adenylate cyclase activity of fat cell ghosts by norepinephrine or fluoride was inhibited by 0.05 mg/ml or greater concentration of tetracycline. Insulin-stimulated glucose oxidation by fat cells was inhibited by 1 mg/ml of tetracycline. These results suggest that the anti-lipolytic action of tetracycline on rat fat cells is secondary to inhibition of cyclic AMP accumulation.

Adenylyl Cyclase Inhibitors↗
PubMed1975

Insulin as an activator of cyclic AMP accumulation in rat fat cells.

In rat fat cells incubated with lipolytic agents and insulin for 30 or 60 minutes the increase in cyclic AMP accumulation due to norepinephrine and theophylline or adenosine deaminase added during the last 2-5 minutes of the incubation period was much greater as compared to cells incubated in the absence of insulin. Protaglandin E1 or nicotinic acid were just as anti-lipolytic as insulin but prior incubation with these agents markedly decreased the subsequent rise in cyclic AMP accumulation due to late catecholamine addition. The ability of insulin to increase cyclic AMP accumulation appeared to be secondary to inhibition of lipolysis. These results indicate that prostaglandin E1 and nicotinic acid are inhibitors of cyclic AMP accumulation while insulin acts by another mechanism to reduce lipolysis.

Adenosine Deaminase↗