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Because several groups have recently questioned a mediating role for cyclic AMP in adrenocortical steroidogenesis, we analysed the problem in more detail by measuring three different cyclic AMP pools in cells isolated from decapsulated rat adrenals. Extra-cellular, total intracellular and bound intracellular cyclic AMP were determined by radioimmunoassay in comparison with corticosterone production induced by low corticotropin concentrations. The increase in extracellular and total intracellular cyclic AMP with low corticotropin concentrations was dependent on the presence of a phosphodiesterase inhibitor and short incubation times. Bound intracellular cyclic AMP was less dependent on these two parameters. In unstimulated cells cyclic AMP bound to its receptor represents only a small fraction of the total intracellular cyclic AMP. After stimulation by a concentration of corticotropin around the threshold for corticosterone production, an increase in bound cyclic AMP was observed which correlated very well with steroidogenesis both temporally and with respect to corticotropin concentration. This finding was complemented by measuring a concomitant decrease in free receptor sites. Full occupancy of the receptors was not necessary for maximal steroidogenesis. Binding kinetics of cyclic [(3)H]AMP in concentrations equivalent to the intracellular cyclic AMP concentration suggest the presence of at least three different intracellular cyclic AMP pools. These observations are in agreement with a possible role for cyclic AMP as a mediator of acute steroidogenesis induced by low corticotropin concentrations.
E J Podesta, and
A Milani, and
H Steffen, and
R Neher
November 1978,
Biochemical and biophysical research communications,
E J Podesta, and
A Milani, and
H Steffen, and
R Neher
September 1977,
Biochemical and biophysical research communications,
E J Podesta, and
A Milani, and
H Steffen, and
R Neher
September 1980,
Biochemical and biophysical research communications,
E J Podesta, and
A Milani, and
H Steffen, and
R Neher
February 1973,
European journal of biochemistry,
E J Podesta, and
A Milani, and
H Steffen, and
R Neher
March 1972,
Science (New York, N.Y.),
E J Podesta, and
A Milani, and
H Steffen, and
R Neher
February 1975,
Biochimica et biophysica acta,
E J Podesta, and
A Milani, and
H Steffen, and
R Neher
January 1972,
Postepy biochemii,
E J Podesta, and
A Milani, and
H Steffen, and
R Neher
January 1994,
Glia,
E J Podesta, and
A Milani, and
H Steffen, and
R Neher
January 1975,
Cancer research,
E J Podesta, and
A Milani, and
H Steffen, and
R Neher
September 1978,
Molecular & general genetics : MGG,
