scholarly journals Steroidogenic action of calcium ions in isolated adrenocortical cells

1980 ◽  
Vol 186 (2) ◽  
pp. 391-397 ◽  
Author(s):  
Ernesto J. Podesta ◽  
Alfred Milani ◽  
Hans Steffen ◽  
Robert Neher
Keyword(s):  
Cyclic Amp ◽  
Adenylate Cyclase ◽  
Cellular Uptake ◽  
Calcium Ions ◽  
Cell Uptake ◽  
Isolated Cells ◽  
Adrenocortical Cells ◽  
Transport Inhibitor ◽  
Receptor Sites ◽  
Isolated Rat

The corticotropin-induced increase of total intracellular and receptor-bound cyclic AMP in isolated rat adrenocortical cells was strictly dependent on extracellular Ca2+. A rise in bound cyclic AMP with rising Ca2+ concentrations was accompanied by a decrease in free cyclic AMP-receptor sites. A Ca2+-transport inhibitor abolished the rise in bound cyclic AMP induced by corticotropin. These data suggested that during stimulation by corticotropin some Ca2+ has to be taken up in order to promote the rise of the relevant cyclic AMP pool. In agreement with this view, adenylate cyclase activity from isolated cells proved also to be dependent on a sub-millimolar Ca2+ concentration in the presence of corticotropin and GTP. When cells were treated under specific conditions, corticosterone production could be activated by Ca2+ in the absence of corticotropin (cells primed for Ca2+). Ca2+-induced steroidogenesis of these cells, in the absence of corticotropin, was also accompanied by an increase in total intracellular and receptor-bound cyclic AMP, as was found previously with corticotropin-induced steroidogenesis in non-primed cells. Calcium ionophores increasing the cell uptake of Ca2+ were not able, however, to increase the cyclic AMP pools in non-primed cells, unlike corticotropin in nonprimed cells or Ca2+ in cells primed for Ca2+. It was concluded that during stimulation by either corticotropin or Ca2+ a possible cellular uptake of Ca2+ must be very limited and directed to a specific site which may affect the coupling of the hormone-receptor–adenylate cyclase complex.

Renal metabolism of N6,O2'-dibutyryl adenosine 3',5'-monophosphate

1979 ◽  
Vol 237 (1) ◽  
pp. F75-F84
Author(s):  
R. Coulson ◽  
W. W. Harrington
Keyword(s):  
Protein Kinase ◽  
Cyclic Amp ◽  
Adenylate Cyclase ◽  
Urinary Excretion ◽  
Rat Kidney ◽  
Bond Cleavage ◽  
Dibutyryl Cyclic Amp ◽  
Renal Metabolism ◽  
Phosphate Bond ◽  
Isolated Rat

Metabolism of dibutyryl cyclic AMP was studied by including the 3H- or C-labeled nucleotide (0.1 mM, 5 mumol) in the recirculating perfusate of the isolated rat kidney. Kidneys were perfused with nucleotide for 60 min. Dibutyryl cyclic AMP was almost completely cleared from the perfusate, about one-quarter as urinary excretion principally by probenecid-sensitive secretion and about one-half as metabolism beyond 3'-phosphate bond cleavage. The principal metabolite, N6-monobutyryl adenosine, accounted for one-third of added dibutyryl cyclic AMP. The remaining metabolites were ATP, ADP AMP, and N6-monobutyryl AMP. Dibutyryl cyclic AMP (0.1 or 1.0 mM) elevated renal ATP but did not alter uricogenesis. Both dibutyryl cyclic AMP and cyclic AMP at 0.2 mM produced similar activation and subcellular redistribution of renal protein kinase. N6-monobutyryl adenosine, unlike adenosine, had no effect on the renal activity of adenylate cyclase, low Km cyclic AMP phosphodiesterase, and protein kinase. Dibutyryl cyclic AMP is like exogenous cyclic AMP in that it penetrates the rat kidney, activates protein kinase, and is metabolized to ATP (R. Coulson, J. Biol. Chem. 251: 4958-4967, 1976), but is unlike cyclic AMP in its extent of secretion and metabolism to ATP and urate and in its formation of the unique metabolites N6-monobutyryl AMP and N6-monobutyryl adenosine.

scholarly journals Ultrastructural changes induced by ACTH in normal adrenocortical cells in culture.

1977 ◽  
Vol 72 (3) ◽  
pp. 757-763 ◽  
Author(s):  
A T Suyama ◽  
J A Long ◽  
J Ramachandran
Keyword(s):  
Cyclic Amp ◽  
Calcium Ions ◽  
Monolayer Culture ◽  
Ultrastructural Changes ◽  
Dibutyryl Cyclic Amp ◽  
Adrenocortical Cells ◽  
Adult Rats ◽  
Adrenal Cells ◽  
Camp Synthesis ◽  
High Concentrations

The effects of ACTH, its o-nitrophenyl sulfenyl derivative (NPS-ACTH) and dibutyryl cyclic AMP (dbc AMP) on the ultrastructural morphology of adrenocortical cells of adult rats in monolayer culture have been investigated. NPS-ACTH, which has previously been shown to stimulate steroidogenesis but not cAMP synthesis in adrenal cells, induced the same characteristic transformation of mitochondrial architecture as produced by ACTH or high concentrations of dbcAMP. All three agents caused the disappearance of electron-opaque granules present in the mitochondria of unstimulated cells. It was found that these granules could be extracted with EGTA (ethylene glycol-bis(beta-aminoethyl ether) N,N,N',N'-tetraacetate). These results are discussed in the light of the known importance of calcium ions in the actions of ACTH.

scholarly journals The cytochemical localization of adenylate cyclase: fact or artifact?

1978 ◽  
Vol 26 (4) ◽  
pp. 298-312 ◽  
Author(s):  
H J Kempen ◽  
J J de Pont ◽  
S L Bonting ◽  
A M Stadhouders
Keyword(s):  
Particulate Matter ◽  
Cyclic Amp ◽  
Adenylate Cyclase ◽  
Lead Nitrate ◽  
Acinar Cells ◽  
Cyclase Activity ◽  
Adenylate Cyclase Activity ◽  
Pancreatic Acinar Cells ◽  
Rat Pancreas ◽  
Isolated Rat

In a study of the location of adenylate cyclase activity in rat pancreas with the method of Reik et al. (Science 168:382, 1970), as modified by Howell and Whitfield (J Histochem Cytochem 20:873, 1972) it was found that (a) unspecific staining occurs in rat pancreatic tissue fragments incubated in the Reik-Howell medium in the absence of substrate; (b) addition of adenylyl-imidodiphosphate (AMP-PNP) as substrate, either alone or together with stimulants of rat pancreas adenylate cyclase (secretin. NaF), does not result in increased precipitation; (c) cytochemical incubation of isolated rat pancreatic acinar cells and of rat liver and kidney fragments does not lead to substrate-specific precipitation. In subsequent chemical studies we have found that cyclic adenosine monophosphate (AMP) formation from [alpha32P]AMP-PNP in the presence of rat pancreatic particulate matter is very low in the Reik-Howell medium without lead ions, but is stimulated by addition of lead nitrate (4 mM). Whereas heat-treatment of the particulate matter abolishes all cyclic AMP formation in the absence of lead ions, it actually increases cyclic AMP production in the presence of 4 mM lead nitrate. This indicates that the cyclic AMP formation in the complet Reik-Howell medium occurs by a nonenzymatic mechanism. In addition, this medium shows a tendency to become turbid, particularly when calcium ions are added to the medium, suggesting a possible explanation for the apparently specific cytochemical detection observed by other authors. A revised cytochemical medium, with barium replacing lead and with a pH of 8.9 (optimal for adenylate cyclase with AMP-PNP substrate), leaves rat pancreatic adenylate cyclase activity intact and hormone sensitive, while it is still able to precipitate imidodiphosphate. However, cytochemical incubation of isolated rat pancreatic acinar cells in this revised medium in the presence of AMP-PNP and secretin does not yield an electron-dense precipitate, showing that the enzyme activity is to low to produce sufficient imidodiphosphate. These findings throw further doubt on the validity of the cytochemical detection of adenylate cyclase, reported by other investigators, notwithstanding the alleged positive results.

MODULATION OF CYCLIC AMP IN ISOLATED RAT UTERINE TISSUE SLICES BY PORCINE RELAXIN

1980 ◽  
Vol 87 (1) ◽  
pp. 153-159 ◽  
Author(s):  
D. G. JUDSON ◽  
SARAH PAY ◽  
K. D. BHOOLA
Keyword(s):  
Cyclic Amp ◽  
Adenylate Cyclase ◽  
Time Course ◽  
Tissue Concentration ◽  
Uterine Tissue ◽  
Tissue Slices ◽  
Rat Uterus ◽  
Hormonal Action ◽  
Isolated Rat

Porcine relaxin produced a rapid, dose-related rise of cyclic AMP values in rat uterine tissue incubated in vitro. In time-course experiments, peak cyclic AMP concentrations were observed in the uterine slices at 5 min; subsequently the values fell, at first rapidly and then more slowly with the tissue concentration remaining significantly raised at 15 min. Levels of cyclic GMP in the same tissue slices were not significantly altered by relaxin. Furthermore, no increase in basal cyclic AMP values was measured in control slices prepared from the rat heart or jejunum. An increase in cyclic AMP concentration comparable to that found in the rat uterus was observed in slices of porcine uterus and cervix but not of vagina when they were stimulated with porcine relaxin. Our results suggest that the hormonal action of relaxin on the uterus and cervix is mediated through receptors linked to the enzyme, adenylate cyclase.

scholarly journals Effects of ACTH (corticotropin) analogues on steroidogenesis and cyclic AMP in rat adrenocortical cells. Evidence for two different steroidogenically responsive receptors

1980 ◽  
Vol 186 (2) ◽  
pp. 599-603 ◽  
Author(s):  
A F Bristow ◽  
C Gleed ◽  
J L Fauchère ◽  
R Schwyzer ◽  
D Schulster
Keyword(s):  
Cyclic Amp ◽  
Mechanism Of Action ◽  
Comparative Studies ◽  
Adrenocortical Cells ◽  
Competitive Antagonist ◽  
Adrenal Cells ◽  
The Relationship ◽  
Isolated Rat

Comparative studies on the mechanism of action of ACTH1-39 and ACTH5-24 [corticotropin-(1-39)- and corticotropin-(5-24)-peptides] on isolated rat adrenal cells were performed. The relationship between stimulated steroidogenesis and cyclic AMP was very different, suggesting that cyclic AMP does not play the same role in mediating the action of the two agonists. Data from three separate experiments showed that the competitive antagonist ACTH6-24 [corticotropin-(6-24)-peptide] had mean inhibitor constants of 13.4 +/- 3.1 nM against ACTH1-39 and 3.4 +/- 1.0 nM against ACTH5-24, indicating that the steroidogenic actions of these two agonists are mediated by two different receptor types. We conclude that there are two possible mechanisms for corticotropin action, only one of which involves the necessary production of cyclic AMP.

scholarly journals Steroidogenesis in isolated adrenocortical cells. Correlation with receptor-bound adenosine 3′:5′-cyclic monophosphate

1979 ◽  
Vol 180 (2) ◽  
pp. 355-363 ◽  
Author(s):  
Ernesto J. Podesta ◽  
Alfred Milani ◽  
Hans Steffen ◽  
Robert Neher
Keyword(s):  
Cyclic Amp ◽  
Phosphodiesterase Inhibitor ◽  
Binding Kinetics ◽  
Adrenocortical Cells ◽  
Mediating Role ◽  
Receptor Sites ◽  
Rat Adrenals ◽  
Two Parameters ◽  
Kinetics Of ◽  
Full Occupancy

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 [3H]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.

Sign in / Sign up

Export Citation Format

Share Document