0013-7227/78/1024-1061$02.00/0 Endocrinology Copyright © 1978 by The Endocrine Society
Vol. 102, No. 4 Printed in U.S.A.
Further Studies on the Relationship between Potassium and Sodium Levels and Adrenocortical Activity* M. VICTORIA LOBO, ELISA T. MARUSIC,f AND GRETI AGUILERA Department of Physiology and Biophysics, University of Chile, School of Medicine, Casilla 6524, Santiago, Chile ABSTRACT. Steroid production in vitro by dog adrenal cortical slices was measured in the presence of varying concentrations of sodium and potassium ions. Increasing concentrations of potassium produced a signincant increase in the intracellular potassium content and in the rate of synthesis of aldosterone. However, the potassium effect on aldosterone secretion may also occur without changes in tissue potassium content. Ouabain significantly diminished intracellular potassium content, but inhibited aldosterone production only at the high dose of 2.5 X 10~3 M in the presence of an elevated external potassium level. Physiological changes in sodium concentration can modify aldosterone pro-
duction. The effect was observed with changes as small as 10 mEq/liter sodium. Changes in external potassium and sodium levels modulate aldosterone as well as corticosterone, but not cortisol production. No changes in the intracellular content of potassium were detectable in angiotensin-stimulated tissue. Nevertheless, high doses of ouabain blocked angiotensin-stimulated aldosterone production without affecting cortisol production. The dissociation observed between intracellular potassium levels and aldosterone production suggests that there is not a simple relationship between the two parameters. (Endocrinology 102: 1061, 1978)
I
T IS well recognized that one of the most been shown by us and by others that this potent stimuli of aldosterone secretion is animal has a very sensitive response to aldosa negative sodium balance. Many studies have terone stimulation (11-13). The direct effect been conducted on the relationship of the of either sodium or potassium ions was exrenin-angiotensin system to the control of al- amined by changing their concentration in the dosterone secretion (1-3). On the other hand, incubation media in the presence or absence there is some evidence that changes in plasma of angiotensin II and/or ouabain. A possible sodium levels may induce direct alterations relation between the intracellular potassium of aldosterone secretion (4-6). Several studies content and the aldosterone response was also have also defined an important role for the investigated. potassium ion in the regulation of aldosterone Material and Methods biosynthesis (7-9). Attempts have been made to relate all of Preparation of the tissue these aldosterone regulatory factors to the The studies were carried out on slices of dog intracellular potassium content (10). Howadrenal cortex. Male mongrel dogs were kept on a ever, it is not certain whether the changes in regular diet containing 50 mEq of sodium daily steroid secretion are mediated by changes in (normal sodium diet). The animals were anestheintracellular potassium content or whether the tized with pentobarbital, the adrenal glands immeglomerulosa cells respond directly to changes diately removed, freed of fat, and washed in chilled in extracellular potassium concentration. isotonic saline solution. Adrenal cortex tissue was The present studies were undertaken to de- obtained by dissection of the gland on a glass dish termine the separate influences of potassium placed on ice and covered with filter paper moistand sodium ions on aldosterone production in ened with cold saline. The first (outer) slice was vitro. Dog adrenal slices were used throughout considered to be mainly the glomerulosa zone. Septhe experimental procedure because it has aration of the zones was not complete; however, it Received April 11, 1977. * This work was supported by Scientific Development Program Grant 3300, University of Chile. t To whom requests for reprints should be addressed.
appeared that very little of the fasciculata zone was present in the outer slices, because the amount of cortisol synthesized was less than one third that of aldosterone. Only outer slices (glomerulosa zone)
1061
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1062
Kndo • 1978 Vol 102 • No 4
LOBO, MARUSIC, AND AGUILERA
were incubated, unless otherwise specified. The slices were cut into small pieces, blotted, and weighed. The slices obtained from each animal were distributed among all the experimental flasks, in order to obtain uniformity. About 60-80 mg tissue were added to each flask. At least two flasks were incubated and analyzed separately for each part of one experiment. The tissues were kept chilled until the incubation was started. Incubation procedure A modified Krebs-Ringer-bicarbonate-glucose soltuion was employed, containing 143 mEq/liter sodium and 4.7 mEq/liter potassium. Tissues were preincubated for 30 min at 37 C under 95% O2-5% CO2 in a Dubnoff metabolic shaker. At the end of the preincubation period the slices were transferred to flasks containing 5 ml fresh medium. The incubation period was 30 min. (Previous experiments have shown linearity of aldosterone production up to 60 min.) Potassium and sodium were maintained at the concentrations noted above, unless otherwise specified. When necessary, the concentrations of potassium and sodium in the media were varied by using more or less chloride salt. Methods for electrolyte measurement At the end of the experiments the adrenal slices were removed from the incubation medium, immediately blotted on filter paper, and placed in a weighing bottle. After weighing, the samples were dried for 72 h at 95-100 C to constant weight (dry weight). The fat content was measured after the dry weight was obtained. Ten milliliters of diethyl ether were added to each bottle and left at room temperature overnight. The solvent was then replaced with 5 ml ether and allowed to remain at room temperature for 2 h. Ether was replaced again and the tissue was dried at 95-98 C for 2 h and reweighed; this procedure allowed the calculation of fat-free tissue solids (FFTS). An average value of 9.6 ± 1.1 (SE)% fat was obtained in the outer slices and 23.1 ± 3.0% in the middle slices (fasciculata zone), even though some dog adrenals have much lower values. The potassium content of the tissues was measured by flame photometry after the samples were ashed in a muffle furnace at 550 C. Duplicate samples of each tissue were measured in an Eppendorf flame photometer. The assay of potassium in six replicate samples from pooled adrenal tissue gave a variation of 6.3% from the highest value to the lowest value.
In parallel samples, the extracellular space (inulin space) of the tissue was estimated in order to calculate the potassium concentration in the intracellular fluid. In these experiments the adrenal slices were incubated in the presence of 0.2 /iCi [14C]inulin (SA, 1.8 mCi/g). At the end of the incubation, the tissue was separated from the medium by filtration. The extracellular compartment was calculated according to Wellen and Benraad (14). The average intracellular potassium content was 142 ± 1 1 mEq/kg water in the outer slices and 149 ± 1 5 mEq/kg water in the middle slices, when the electrolyte content was measured immediately after removal of the glands. Means and SD were determined for six glands. Methods for steroid measurement After the incubation, the medium was acidified with 0.05 ml 0 . 1 M acetic acid and kept frozen until the extraction. An aliquot was extracted with methylene chloride after the addition of 8,000 dpm (24 pg) [l,2-3H]aldosterone, 11,000 dpm (32 pg) [1,2-3H]corticosterone and 11,000 dpm (33 pg) [1,2-3H]cortisol. After extraction, the samples were washed sequentially with O.i vol 0.1 M NaOH, 0.1 M acetic acid and twice-distilled water. The extract was then chromatographed by using the Bush B5 system in order to separate and purify the steroids. Aldosterone, corticosterone, and cortisol were measured by radioimmunoassay. The method described for plasma steroids by Underwood and Williams (15) was employed in our laboratory for human and dog plasmas (12). All samples were analyzed in duplicate. Antisera to aldosterone and corticosterone were a gift from Dr. Gordon H. Williams and the characterization of these has been described by Underwood and Williams (15). The antiserum to cortisol and all the radioactive compounds were purchased from New England Nuclear. All values are expressed as nanograms steroid/ h/100 mg outer cortex tissue. Levels of significance between means were assessed by using Student's t test for paired values. Simultaneous assessment of multiple comparisons was also performed by analysis of variance (16). Angiotensin II was kindly supplied by Ciba. It was dissolved just before use.
Results Steroid response to increasing concentrations of potassium Studies were first conducted to establish the effect, in vitro, of potassium ions on steroid
The Endocrine Society. Downloaded from press.endocrine.org by [${individualUser.displayName}] on 16 November 2015. at 18:14 For personal use only. No other uses without permission. . All rights reserved.
K+ AND N A + LEVELS AND ADRENAL STEROIDS production by dog adrenal glands. Subsequently, the influences of several factors on the potassium stimulus were studied. The effects of changes in the levels of extracellular potassium on the production of corticoids by outer slices of dog adrenal cortex are summarized in Fig. 1. Modifications of potassium levels in the range of 1.5-12 mEq/liter were able to change significantly aldosterone production. The effect of potassium on corticosterone production was similar to that of aldosterone, but the increments in corticosterone synthesis were smaller than those of aldosterone. When the concentration of potassium in the incubation medium was increased above 12 mEq/liter (up to 18 mEq/liter K), there was a drop in both aldosterone and corticosterone production rates. No significant modification in the level of cortisol synthesis was observed with any change in the potassium concentration. The concentration of potassium at which maximal stimulation of steroid production occurs in dog adrenals is different from that found in rat glands. In parallel experiments performed with rat adrenal quarters, the maximal effect on aldosterone production was obtained when the potassium concentration was 9 mEq/liter, confirming the results of others with the same tissue. In two experiments per-
1063
formed with rats kept on a normal sodium diet, the mean aldosterone production was 795, 1955, and 1470 ng/100 mg tissue/h when the potassium level was 3,9, and 12 mEq/liter, respectively. The mean plasma potassium level in our population of mongrel dogs was 4.7 ± 0.2 mEq/liter. Therefore, we consider that value as normal, and take it as the control level. All subsequent experiments were done with a Krebs-Ringer-bicarbonate-glucose medium containing 4.7 mEq/liter K as the control sample. Intracellular potassium content and the effect ofouabain on aldosterone production The intracellular potassium concentration of outer adrenal slices was measured under different conditions. A relationship between extracellular potassium, tissue potassium content, and aldosterone production was found as indicated in Fig. 2. The effect of ouabain on both parameters is shown in the same figure. A concentration of 2.5 X 10~3 M ouabain caused a significant reduction in the intracellular potassium levels under all conditions assayed. Nevertheless, aldosterone production was only reduced by ouabain when 7.5 mEq/liter potassium was present. Further-
400
o o
3
300
Q- £ O
200
- 2 2 ^ 100 UJ C \^ CO
1.5
3.0
4.7
6.0
7.5
9.0
12.0
14.0
18.0
POTASSIUM (meq / I ) FIG. 1. Comparison between aldosterone (open bar), corticosterone (hatched bar), and cortisol (closed bar) production in dog adrenal slices incubated with different concentrations of potassium. Means ± SE of aldosterone (n = 5) and corticosterone (n = 3). Analysis of variance revealed a significant effect of potassium on aldosterone production (F8,.ie = 180.7, P< 0.001) and on corticosterone production (F8,i8 = 62.2, P< 0.001). The mean value of cortisol was measured in two experiments.
The Endocrine Society. Downloaded from press.endocrine.org by [${individualUser.displayName}] on 16 November 2015. at 18:14 For personal use only. No other uses without permission. . All rights reserved.
200
CH
CONTROL
^
OUABAIN
I 50 ~
100
UJ
o 1978 Vol 102 « No 4
Scoggins, In vivo effects of ouabain on aldosterone
24. 25. 26.
27.
28.
29.
30.
31.
32.
33.
and cortisol secretion in conscious sheep, Endocrinology 94: 1304, 1974. Hales, C. N., and R. D. E. Milner, The role of sodium and potassium in insulin secretion from rabbit pancreas, JPhysiol (Lond) 194: 725, 1968. Dicker, S. E., Release of vasopressin and oxytocin from isolated pituitary glands of adult and new-born rats, J Physiol (Lond) 185: 429, 1966. Fleischer, N., G. Zimmermman, W. Schindler, and M. Hutchins, Stimulation of adrenocorticotropin (ACTH) and growth hormone (GH) release by ouabain: relationship to calcium, Endocrinology 91:1436, 1972. Saruta, T., R. Cook, and N. M. Kaplan, Adrenocortical steroidogenesis: studies on the mechanism of action of angiotensin and electrolytes, J Clin Invest 51: 2239, 1972. Mendelsohn, F. A., and C. Mackie, Relation of intracellular K+ and steroidogenesis in isolated adrenal zona glomerulosa and fasciculate cells, Clin Sci Mol Med 49: 13, 1975. Munday, K. A., B. J. Parsons, and J. A. Poat, The effect of angiotensin on cation transport by rat kidney cortex slices, JPhysiol (Lond) 215: 269,1971. Szalay, K., Inhibiting effect of angiotensin on potassium accumulation of adrenal cortex, Biochem Pharmacol 18: 962, 1969. Healy, J. K., A. J. Elliott, and L. C. Harrison, Effects of angiotensin on plasma electrolyte concentrations in rabbits and in man, Clin Sci Mol Med 46: 19, 1974. Fredlund, P., S. Saltman, T. Kondo, J. Douglas, and K. J. Catt, Aldosterone production by isolated glomerulosa cells: modulation of sensitivity to angiotensin II and ACTH by extracellular potassium concentration, Endocrinology 100: 481, 1977. Sayers, G., R. J. Beall, and S. Seelig, Isolated adrenal cells: adrenocorticotropic hormone, calcium, steroidogenesis, and cyclic adenosine monophosphate, Science 175: 1131,1972.
The Endocrine Society. Downloaded from press.endocrine.org by [${individualUser.displayName}] on 16 November 2015. at 18:14 For personal use only. No other uses without permission. . All rights reserved.
Vol. 102, No. 4 Printed in U.S.A.
Further Studies on the Relationship between Potassium and Sodium Levels and Adrenocortical Activity* M. VICTORIA LOBO, ELISA T. MARUSIC,f AND GRETI AGUILERA Department of Physiology and Biophysics, University of Chile, School of Medicine, Casilla 6524, Santiago, Chile ABSTRACT. Steroid production in vitro by dog adrenal cortical slices was measured in the presence of varying concentrations of sodium and potassium ions. Increasing concentrations of potassium produced a signincant increase in the intracellular potassium content and in the rate of synthesis of aldosterone. However, the potassium effect on aldosterone secretion may also occur without changes in tissue potassium content. Ouabain significantly diminished intracellular potassium content, but inhibited aldosterone production only at the high dose of 2.5 X 10~3 M in the presence of an elevated external potassium level. Physiological changes in sodium concentration can modify aldosterone pro-
duction. The effect was observed with changes as small as 10 mEq/liter sodium. Changes in external potassium and sodium levels modulate aldosterone as well as corticosterone, but not cortisol production. No changes in the intracellular content of potassium were detectable in angiotensin-stimulated tissue. Nevertheless, high doses of ouabain blocked angiotensin-stimulated aldosterone production without affecting cortisol production. The dissociation observed between intracellular potassium levels and aldosterone production suggests that there is not a simple relationship between the two parameters. (Endocrinology 102: 1061, 1978)
I
T IS well recognized that one of the most been shown by us and by others that this potent stimuli of aldosterone secretion is animal has a very sensitive response to aldosa negative sodium balance. Many studies have terone stimulation (11-13). The direct effect been conducted on the relationship of the of either sodium or potassium ions was exrenin-angiotensin system to the control of al- amined by changing their concentration in the dosterone secretion (1-3). On the other hand, incubation media in the presence or absence there is some evidence that changes in plasma of angiotensin II and/or ouabain. A possible sodium levels may induce direct alterations relation between the intracellular potassium of aldosterone secretion (4-6). Several studies content and the aldosterone response was also have also defined an important role for the investigated. potassium ion in the regulation of aldosterone Material and Methods biosynthesis (7-9). Attempts have been made to relate all of Preparation of the tissue these aldosterone regulatory factors to the The studies were carried out on slices of dog intracellular potassium content (10). Howadrenal cortex. Male mongrel dogs were kept on a ever, it is not certain whether the changes in regular diet containing 50 mEq of sodium daily steroid secretion are mediated by changes in (normal sodium diet). The animals were anestheintracellular potassium content or whether the tized with pentobarbital, the adrenal glands immeglomerulosa cells respond directly to changes diately removed, freed of fat, and washed in chilled in extracellular potassium concentration. isotonic saline solution. Adrenal cortex tissue was The present studies were undertaken to de- obtained by dissection of the gland on a glass dish termine the separate influences of potassium placed on ice and covered with filter paper moistand sodium ions on aldosterone production in ened with cold saline. The first (outer) slice was vitro. Dog adrenal slices were used throughout considered to be mainly the glomerulosa zone. Septhe experimental procedure because it has aration of the zones was not complete; however, it Received April 11, 1977. * This work was supported by Scientific Development Program Grant 3300, University of Chile. t To whom requests for reprints should be addressed.
appeared that very little of the fasciculata zone was present in the outer slices, because the amount of cortisol synthesized was less than one third that of aldosterone. Only outer slices (glomerulosa zone)
1061
The Endocrine Society. Downloaded from press.endocrine.org by [${individualUser.displayName}] on 16 November 2015. at 18:14 For personal use only. No other uses without permission. . All rights reserved.
1062
Kndo • 1978 Vol 102 • No 4
LOBO, MARUSIC, AND AGUILERA
were incubated, unless otherwise specified. The slices were cut into small pieces, blotted, and weighed. The slices obtained from each animal were distributed among all the experimental flasks, in order to obtain uniformity. About 60-80 mg tissue were added to each flask. At least two flasks were incubated and analyzed separately for each part of one experiment. The tissues were kept chilled until the incubation was started. Incubation procedure A modified Krebs-Ringer-bicarbonate-glucose soltuion was employed, containing 143 mEq/liter sodium and 4.7 mEq/liter potassium. Tissues were preincubated for 30 min at 37 C under 95% O2-5% CO2 in a Dubnoff metabolic shaker. At the end of the preincubation period the slices were transferred to flasks containing 5 ml fresh medium. The incubation period was 30 min. (Previous experiments have shown linearity of aldosterone production up to 60 min.) Potassium and sodium were maintained at the concentrations noted above, unless otherwise specified. When necessary, the concentrations of potassium and sodium in the media were varied by using more or less chloride salt. Methods for electrolyte measurement At the end of the experiments the adrenal slices were removed from the incubation medium, immediately blotted on filter paper, and placed in a weighing bottle. After weighing, the samples were dried for 72 h at 95-100 C to constant weight (dry weight). The fat content was measured after the dry weight was obtained. Ten milliliters of diethyl ether were added to each bottle and left at room temperature overnight. The solvent was then replaced with 5 ml ether and allowed to remain at room temperature for 2 h. Ether was replaced again and the tissue was dried at 95-98 C for 2 h and reweighed; this procedure allowed the calculation of fat-free tissue solids (FFTS). An average value of 9.6 ± 1.1 (SE)% fat was obtained in the outer slices and 23.1 ± 3.0% in the middle slices (fasciculata zone), even though some dog adrenals have much lower values. The potassium content of the tissues was measured by flame photometry after the samples were ashed in a muffle furnace at 550 C. Duplicate samples of each tissue were measured in an Eppendorf flame photometer. The assay of potassium in six replicate samples from pooled adrenal tissue gave a variation of 6.3% from the highest value to the lowest value.
In parallel samples, the extracellular space (inulin space) of the tissue was estimated in order to calculate the potassium concentration in the intracellular fluid. In these experiments the adrenal slices were incubated in the presence of 0.2 /iCi [14C]inulin (SA, 1.8 mCi/g). At the end of the incubation, the tissue was separated from the medium by filtration. The extracellular compartment was calculated according to Wellen and Benraad (14). The average intracellular potassium content was 142 ± 1 1 mEq/kg water in the outer slices and 149 ± 1 5 mEq/kg water in the middle slices, when the electrolyte content was measured immediately after removal of the glands. Means and SD were determined for six glands. Methods for steroid measurement After the incubation, the medium was acidified with 0.05 ml 0 . 1 M acetic acid and kept frozen until the extraction. An aliquot was extracted with methylene chloride after the addition of 8,000 dpm (24 pg) [l,2-3H]aldosterone, 11,000 dpm (32 pg) [1,2-3H]corticosterone and 11,000 dpm (33 pg) [1,2-3H]cortisol. After extraction, the samples were washed sequentially with O.i vol 0.1 M NaOH, 0.1 M acetic acid and twice-distilled water. The extract was then chromatographed by using the Bush B5 system in order to separate and purify the steroids. Aldosterone, corticosterone, and cortisol were measured by radioimmunoassay. The method described for plasma steroids by Underwood and Williams (15) was employed in our laboratory for human and dog plasmas (12). All samples were analyzed in duplicate. Antisera to aldosterone and corticosterone were a gift from Dr. Gordon H. Williams and the characterization of these has been described by Underwood and Williams (15). The antiserum to cortisol and all the radioactive compounds were purchased from New England Nuclear. All values are expressed as nanograms steroid/ h/100 mg outer cortex tissue. Levels of significance between means were assessed by using Student's t test for paired values. Simultaneous assessment of multiple comparisons was also performed by analysis of variance (16). Angiotensin II was kindly supplied by Ciba. It was dissolved just before use.
Results Steroid response to increasing concentrations of potassium Studies were first conducted to establish the effect, in vitro, of potassium ions on steroid
The Endocrine Society. Downloaded from press.endocrine.org by [${individualUser.displayName}] on 16 November 2015. at 18:14 For personal use only. No other uses without permission. . All rights reserved.
K+ AND N A + LEVELS AND ADRENAL STEROIDS production by dog adrenal glands. Subsequently, the influences of several factors on the potassium stimulus were studied. The effects of changes in the levels of extracellular potassium on the production of corticoids by outer slices of dog adrenal cortex are summarized in Fig. 1. Modifications of potassium levels in the range of 1.5-12 mEq/liter were able to change significantly aldosterone production. The effect of potassium on corticosterone production was similar to that of aldosterone, but the increments in corticosterone synthesis were smaller than those of aldosterone. When the concentration of potassium in the incubation medium was increased above 12 mEq/liter (up to 18 mEq/liter K), there was a drop in both aldosterone and corticosterone production rates. No significant modification in the level of cortisol synthesis was observed with any change in the potassium concentration. The concentration of potassium at which maximal stimulation of steroid production occurs in dog adrenals is different from that found in rat glands. In parallel experiments performed with rat adrenal quarters, the maximal effect on aldosterone production was obtained when the potassium concentration was 9 mEq/liter, confirming the results of others with the same tissue. In two experiments per-
1063
formed with rats kept on a normal sodium diet, the mean aldosterone production was 795, 1955, and 1470 ng/100 mg tissue/h when the potassium level was 3,9, and 12 mEq/liter, respectively. The mean plasma potassium level in our population of mongrel dogs was 4.7 ± 0.2 mEq/liter. Therefore, we consider that value as normal, and take it as the control level. All subsequent experiments were done with a Krebs-Ringer-bicarbonate-glucose medium containing 4.7 mEq/liter K as the control sample. Intracellular potassium content and the effect ofouabain on aldosterone production The intracellular potassium concentration of outer adrenal slices was measured under different conditions. A relationship between extracellular potassium, tissue potassium content, and aldosterone production was found as indicated in Fig. 2. The effect of ouabain on both parameters is shown in the same figure. A concentration of 2.5 X 10~3 M ouabain caused a significant reduction in the intracellular potassium levels under all conditions assayed. Nevertheless, aldosterone production was only reduced by ouabain when 7.5 mEq/liter potassium was present. Further-
400
o o
3
300
Q- £ O
200
- 2 2 ^ 100 UJ C \^ CO
1.5
3.0
4.7
6.0
7.5
9.0
12.0
14.0
18.0
POTASSIUM (meq / I ) FIG. 1. Comparison between aldosterone (open bar), corticosterone (hatched bar), and cortisol (closed bar) production in dog adrenal slices incubated with different concentrations of potassium. Means ± SE of aldosterone (n = 5) and corticosterone (n = 3). Analysis of variance revealed a significant effect of potassium on aldosterone production (F8,.ie = 180.7, P< 0.001) and on corticosterone production (F8,i8 = 62.2, P< 0.001). The mean value of cortisol was measured in two experiments.
The Endocrine Society. Downloaded from press.endocrine.org by [${individualUser.displayName}] on 16 November 2015. at 18:14 For personal use only. No other uses without permission. . All rights reserved.
200
CH
CONTROL
^
OUABAIN
I 50 ~
100
UJ
o 1978 Vol 102 « No 4
Scoggins, In vivo effects of ouabain on aldosterone
24. 25. 26.
27.
28.
29.
30.
31.
32.
33.
and cortisol secretion in conscious sheep, Endocrinology 94: 1304, 1974. Hales, C. N., and R. D. E. Milner, The role of sodium and potassium in insulin secretion from rabbit pancreas, JPhysiol (Lond) 194: 725, 1968. Dicker, S. E., Release of vasopressin and oxytocin from isolated pituitary glands of adult and new-born rats, J Physiol (Lond) 185: 429, 1966. Fleischer, N., G. Zimmermman, W. Schindler, and M. Hutchins, Stimulation of adrenocorticotropin (ACTH) and growth hormone (GH) release by ouabain: relationship to calcium, Endocrinology 91:1436, 1972. Saruta, T., R. Cook, and N. M. Kaplan, Adrenocortical steroidogenesis: studies on the mechanism of action of angiotensin and electrolytes, J Clin Invest 51: 2239, 1972. Mendelsohn, F. A., and C. Mackie, Relation of intracellular K+ and steroidogenesis in isolated adrenal zona glomerulosa and fasciculate cells, Clin Sci Mol Med 49: 13, 1975. Munday, K. A., B. J. Parsons, and J. A. Poat, The effect of angiotensin on cation transport by rat kidney cortex slices, JPhysiol (Lond) 215: 269,1971. Szalay, K., Inhibiting effect of angiotensin on potassium accumulation of adrenal cortex, Biochem Pharmacol 18: 962, 1969. Healy, J. K., A. J. Elliott, and L. C. Harrison, Effects of angiotensin on plasma electrolyte concentrations in rabbits and in man, Clin Sci Mol Med 46: 19, 1974. Fredlund, P., S. Saltman, T. Kondo, J. Douglas, and K. J. Catt, Aldosterone production by isolated glomerulosa cells: modulation of sensitivity to angiotensin II and ACTH by extracellular potassium concentration, Endocrinology 100: 481, 1977. Sayers, G., R. J. Beall, and S. Seelig, Isolated adrenal cells: adrenocorticotropic hormone, calcium, steroidogenesis, and cyclic adenosine monophosphate, Science 175: 1131,1972.
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![[Relationship between urinary sodium and potassium excretion and blood pressure].](/assets/img/hold.png)
