RESUMO
The aim of the present work is to study the effect of cyclic AMP on the metabolism of adipose tissue as well as the effect of cations on the action of cyclic AMP. The epididymal fat pads isolated from the male albino rats were used for this experimental work. The epididymal fat pads were incubated under different condition according to the 8 Schedule presented in table. According to the results obtained in this work, it is apparant that: 1. Addition of cyclic AMP in a dose of 0.2 mM to the incubation medium resulted in a significant antilipolytic effect as well as insignificant changes in glucose uptake and cyclic AMP content in adipose tissue. 2. Addition of Ca[2+] inos to the incubation medium was found to has a non significant changes in glucose uptake by adipose tissue as well as marked antilipolyptic effect. The antilipolytic effect is attributed to the inhibitory effect of Ca[2+] ions on adenyl cyclase enzyme as well as phosphodiesterase enzyme. Ca[2+] ions stimulate the adipose tissue phosphatase enzyme with subsequent inactivation of adipose tissue lipase enzyme. 3. Addition of Mg[2+] ions to the incubation medium, led to a marked antilipolytic effect. This effect was attributed to the presence of; Mg[2+] ions which responsible for the normal function of adenyl cyclase as well as phosphodiesterase enzymes. On the other hand, addition of Mg[2+] ions to the incubation medium resultad in a significant increase in glucose uptake by adipose tissue. This effect may be attributed to the stimulatory effect of Mg[2+] ions on phosphofructok-inase as well as pyruvate kinase enzymes. 4. Addition of K+ inos to the incubation medium led to a significant lipolytic effect. This effect may be attributed to stimulation of adenyl cyclase by K+ ions with subsequent increase in cyclic AMP content in adipose tissue. On the other hand, K+ ions led to a non significant decrease in glucose uptake by adipose tissue. 5. Addition of 0.2mM cyclic AMP to the incubation medium devoid of either Ca[2+] or K+ led to a significant increase in glucose uptake by adipose tissue as well as a mrked lipolytic effect. These effects may be attributed to the fact that Omission of these cations from the incubation medium permits the enterance of cyclic AMP to the adipocytes. It can be concluded from the present work that some cations modulates the effect of cyclic AMP in adipose tissue metabolism. In the presence of Ca[2+] and Mg ions in the incubation medium cyclic AMP has antilipolyic effect. This effect may be due to its conversion to metabolites which inhibit endogenous adenyl cyclase. On the other hand it was found that the addition of K+ ions to the incubation medium led to a significant increase in the rate of lipolysis. This lipolytic effect may be attributed to the associated increase in cyclic AMP content in adipose tissue