Effect of human beta-endorphin on plasma aldosterone concentrations in normal human subjects

A case of unilateral adrenal hyperplasia: the diagnostic dilemma of hyperaldosteronism

OBJECTIVE

To report the successful laparoscopic surgical management of a case of right unilateral adrenal hyperplasia.

METHODS

We present a case of unilateral adrenal hyperplasia and review the pertinent literature. The effectiveness of surgical treatment of unilateral adrenal hyperplasia is evaluated.

RESULTS

A 50-year-old man had a 7-year history of hypertension, which had been treated with antihypertensive medications. On initial assessment, he was taking long-acting diltiazem, 240 mg twice a day, and his blood pressure was 150/84 mm Hg. He was noted to have recurrent hypokalemia, low plasma renin activity, increased plasma aldosterone concentration, and high urinary aldosterone levels. Magnetic resonance imaging of the adrenal glands revealed a normal left adrenal gland and fullness of the right adrenal gland. Selective adrenal vein catheterization showed findings consistent with a right-sided adrenal gradient. Surgical removal of the right adrenal gland laparoscopically alleviated his symptoms and cured his hypertension and hypokalemia. Pathologic examination of the right adrenal gland revealed diffuse hyperplasia of the zona fasciculata and zona reticularis. Plasma aldosterone, renin, and potassium levels returned to normal postoperatively, and his blood pressure declined to 120/70 mm Hg. At 1-year follow-up, the patient remained normotensive without the need for antihypertensive agents.

CONCLUSIONS

This rare type of hyperaldosteronism, known as unilateral adrenal hyperplasia, is difficult to categorize not only because it fails to typify a conventional subtype but also because it is difficult to confirm the pathologic diagnosis. Recognition of the variety of provocative, biochemical, and imaging results that may be seen in this disorder is important in making the correct diagnosis. Determining unilaterality of disease by selective adrenal vein sampling can result in a cure of hypertension and hypokalemia by surgical resection.

Non-ACTH POMC fragments stimulate aldosterone production by human adrenal cells in vitro

The possibility that non-ACTH proopiomelanocortin-derived fragments may stimulate aldosterone production has previously been studied using nonhuman cells with inconsistent results. We have examined the response of aldosterone to beta-endorphin (beta-End) and joining peptide (JP) and compared these with the response to ACTH using eight cell suspensions prepared from human adrenal glands. ACTH, 10(-6), 10(-8), and 10(-10) M, consistently stimulated aldosterone accumulation above that occurring in unstimulated cells (150 +/- 83, 120 +/- 62, and 77 +/- 32 fmol/10(4) cells above basal, respectively; mean +/- SE; p < 0.05). beta-End significantly stimulated aldosterone production at 10(-6) and 10(-8) M (114 +/- 84 and 50 +/- 24 fmol/10(4) cells above basal; p < 0.05); 10(-10) M beta-End did not provide significant stimulation. Furthermore, JP stimulated aldosterone biosynthesis (41 +/- 16 fmol/10(4) cells above basal; p < 0.05), only at the highest concentration used, 10(-6) M. The addition of 10(-8) M ACTH plus 10(-6) and 10(-10) M beta-End to human adrenal cells yielded values significantly greater than those achieved with either agent alone (267 +/- 152 and 183 +/- 89 fmol/10(4) cells above basal; p < 0.05). These data indicate for the first time that beta-End and JP have the capacity to stimulate aldosterone production in human adrenal cells in vitro. The physiological and potential clinical significance of these observations has yet to be elucidated.

The influence of alpha-fluoromethylhistidine and histamine receptor antagonists on the beta-endorphin-induced corticosterone response

Involvement of a central histaminergic mechanism in the stimulating effect of beta-endorphin (beta-End) on the pituitary-adrenocortical activity, measured indirectly through corticosterone secretion, was investigated in conscious rats. The rise in serum corticosterone levels, induced by beta-End injected intraventricularly (icv) was considerably impaired by pretreatment with naltrexone, an opioid receptor antagonist. The stimulating effect of beta-End was almost totally suppressed by a prior icv administration of mepyramine, a histamine H1-receptor antagonist, and also considerably reduced by pretreatment with cimetidine, an H2-receptor antagonist. The strongest suppression, by 83%; of the beta-End-induced corticosterone response was evoked by a prior administration of alpha-fluoromethylhistidine, an inhibitor of neuronal histamine synthesis in the brain. These results indicate that both the brain neuronal histamine and central histamine H1- and H2-receptors are considerably involved in the beta-endorphin-induced stimulation of the pituitary-adrenocortical activity.

Effects of beta-lipotropin, beta-endorphin, gamma 2-melanotropin and corticotropin on steroid production by isolated human adrenocortical cells

Normal human adrenocortical cells (from multi-organ donors) were incubated with corticotropin (tetracosactide), highly purified human beta-lipotropin, synthetic human beta-lipotropin, gamma 2-melanocyte stimulating hormone and beta-endorphin. Corticotropin stimulated cortisol, aldosterone and 18-hydroxycorticosterone production starting at 10(-12)-10(-11) mol/l in normal adrenocortical cells. Purified human beta-lipotropin also stimulated steroidogenesis but 100-1000-fold higher concentrations of the peptide were needed. In contrast, synthetic human beta-lipotropin was without any effect on steroid production up to concentrations of 10(-7) mol/l. Synthetic beta-lipotropin (5 x 10(-10) mol/l) did not significantly change the dose-response curve for corticotropin (10(-13) mol/l-10(-9) mol/l) versus the three steroids measured. gamma 2-Melanotropin and beta-endorphin (10(-6) mol/l) stimulated the secretion of cortisol, but not of aldosterone. Since synthetic human beta-lipotropin has no effect on human adrenocortical cells, the purified beta-lipotropin must be contaminated with traces of corticotropin. Since pathologically elevated levels of proopiomelanocortin-derived peptides will rarely exceed plasma concentrations of 10(-10) mol/l, our findings in vitro do not support a physiological or pathophysiological role of the peptides examined in the regulation of adrenal steroid secretion.