The relation of adenyl cyclase to the activity of other ATP utilizing enzymes and phosphodiesterase in preparations of rat brain; mechanism of stimulation of cyclic AMP accumulation by NaF

Abstract

Sunmmary1. A method for measuring the rate of production of "IC-labelled adenine nucleotides, including cyclic adenosine 3',5'monophosphate (cyclic AMP), from ["IC]-adenosinetriphosphate (ATP) was developed and used to study the effects of ATP, adenosine diphosphate (ADP) and adenosine 5'-monophosphate (AMP) on the rate of accumulation of cyclic AMP in cell-free preparations of adenyl cyclase from rat brain. 2. The mechanism by which NaF increases cyclic AMP accumulation was studied by comparing its effect on adenine nucleotide metabolism with that of an ATP regenerating system.3. ADP and ATP are potent inhibitors of phosphodiesterase (PDE) and it is the sum of the concentrations of these two nucleotides which controlled the rate of destruction of cyclic AMP. The effect of these nucleotides was significant even in the presence of 6-7 mm theophylline; theophylline itself inhibited PDE only 50-60%. 4. Fluoride ion had no direct effect on PDE but it inhibited the rate of hydrolysis of ADP and ATP and thus indirectly inhibited PDE. The effect of fluoride ion on cyclic AMP accumulation can be explained, at least in part, by this indirect inhibition of PDE.5. Studies on a more purified preparation of adenyl cyclase clearly demonstrated a direct action of NaF on adenyl cyclase.

The relation of adenyl cyclase to the activity of other ATP utilizing enzymes and phosphodiesterase in preparations of rat brain; mechanism of stimulation of cyclic AMP accumulation by adrenaline, ouabain and Mn++

“…All these enzyme systems exist in the intact cell and it is not improbable that physiological stimulators of adenyl cyclase act through these systems in the same way as that described for NaF (Katz & Tenenhouse, 1973).…”

“…Butcher & Sutherland (1967) as described previously (Katz & Tenenhouse, 1973) except in some experiments where equimolar amounts of Mn + + were substituted for Mg++ in the media used.…”

“…The rat cerebral cortex preparation of adenyl cyclase was prepared as described previously (Katz & Tenenhouse, 1973).…”

“…In previous studies (Katz & Tenenhouse, 1973), it was shown that in cell-free preparations of adenyl cyclase an effect on other enzyme systems can result in a net accumulation of cyclic adenosine 3',5'-monophosphate (cyclic AMP). All these enzyme systems exist in the intact cell and it is not improbable that physiological stimulators of adenyl cyclase act through these systems in the same way as that described for NaF (Katz & Tenenhouse, 1973).…”

“…In this study, in which the method of adenine nucleotide deternination previously described by Katz & Tenenhouse (1973) was used, an attempt was made to elucidate the nature of the stimulation of adenyl cyclase by adrenaline and ouabain in the presence of Mn + + and Mg++.…”