Effect of histamine on the adrenal secretion of cortisol and corticosterone in hypophysectomized dogs

Altered methylprednisolone pharmacodynamics in healthy subjects with histamine N-methyltransferase C314T genetic polymorphism

This study investigated the potential differences in methylprednisolone pharmacodynamics between healthy subjects with different histamine N-methyltransferase (HNMT) C314T genotypes. Six individuals with C/C genotype and 4 with C/T genotype were administered a single intravenous dose of methylprednisolone 0.6 mg/kg ideal body weight in a randomized 2-period manner. Methylprednisolone plasma concentrations were fitted with a 1-compartment model. Cortisol and whole blood histamine suppression were assessed by indirect response models, with circadian baseline cortisol analyzed by Fourier analysis. The area between the baseline and effect curve and the area under the effect versus time curve suppression ratio were used to characterize plasma histamine suppression. Methylprednisolone pharmacokinetics and plasma and whole blood histamine suppression were similar between the 2 genotype groups. Median nadir of cortisol and the 50% inhibitory concentration for cortisol were significantly higher in subjects with C/T genotype than those with C/C genotype (P=.031 and .033, respectively, Wilcoxon rank sum test). Subjects who are heterozygous for the T314 variant allele thus appeared less sensitive to the suppressive effects of methylprednisolone on cortisol secretion.

Endogenous glucocorticoids and antigen-induced acute and late phase pulmonary responses

BACKGROUND

Several studies suggest that endogenous glucocorticoids can dampen the severity of experimental allergic reactions in animals.

OBJECTIVE

To investigate the influence that endogenous glucocorticoids have on the course of IgE-mediated pulmonary early and late phase reactions.

METHODS

Twenty-one allergic asthmatic and six healthy control subjects underwent inhaled antigen challenge with measurements of plasma cortisol and cortisone by gas chromatography-mass spectrometry.

RESULTS

There were no differences between the asthmatic and control groups in the baseline levels of cortisol or cortisone. However, the asthmatic subjects had significantly higher cortisol levels (67.2 +/- 8.6 vs 35.1 +/- 4.5 ng/mL; P = 0.04) and had higher cortisol/cortisone ratios (4.8 +/- 0. 6 vs 3.0 +/- 0.2; P = 0.01) 8 h after challenge compared to the control subjects. Among the asthmatic subjects, those whose FEV1 recovered rapidly had higher baseline levels of cortisol and those who displayed a late phase reaction had lower levels of cortisol during the late phase period.

CONCLUSION

The results suggest that endogenous glucocorticoids may play a significant role in the modulation of airway responses to antigen challenge, and that antigen challenge may induce cortisol production in allergic subjects.

H1 action of histamine on aldosterone and cortisol secretion by perfused dog adrenal

The left adrenal of hypophysectomized-nephrectomized dogs was perfused in situ with artificial medium equilibrated with 95% O2-5% CO2. Repeated secretory responses of aldosterone to ACTH and histamine were almost reproducible during 2 h of perfusion, but those of cortisol and corticosterone gradually reduced. The secretion of aldosterone in response to histamine markedly increased at 1 microM and those of cortisol and corticosterone significantly increased at 1 and 10 microM, respectively. The secretory response of aldosterone to 10 microM histamine was comparable with that to 300 microU/ml ACTH, but the secretory responses of cortisol and corticosterone to 10 microM histamine were very much lower than those to 1 microU/ml ACTH. The secretory responses of these three steroids to 10 microM histamine were almost completely depressed by continuous administration of 10 microM pyrilamine maleate, but not abolished by that of 100 microM metiamide. The secretory responses of these three steroids to 10 microM histamine were slightly depressed by continuous infusion of 10 microM methysergide maleate. These results suggest that histamine at pathophysiological concentrations stimulates the secretion of aldosterone markedly, and those of cortisol and corticosterone slightly, via an H1 receptor of adrenocortical cells in the dog.

Pituitary-dependent and -independent secretion of CS caused by bacterial endotoxin in rats

Injection of bacterial endotoxin [lipopolysaccharide (LPS)] or immobilization stress increased serum levels of ACTH with a concomitant increase in the levels or corticosterone (CS) of rats. LPS also caused a significant increase in the serum CS levels of hypophysectomized rats. In contrast, immobilization stress-induced CS release was abolished completely in these rats. Injection of histamine, a possible mediator of LPS-induced CS secretion, provoked a significant increase in the serum CS levels of hypophysectomized rats. Neither histamine nor LPS had any appreciable effect on production or release of CS by cultured adrenal cells. These results suggest that LPS-induced CS secretion is largely dependent on hypophysial ACTH release but it also depends, in part, on an extrapituitary mechanism and that the LPS-induced pituitary-independent secretion of CS is mediated by histamine produced in the peripheral tissues. On the other hand, stress-provoked CS secretion is absolutely dependent on the pituitary-adrenocortical system.

Effect of histamine on blood flow to the adrenal glands of pigs

Blood flow to the adrenal glands was measured with radioactive microspheres labeled with 85Sr in 25-37 kg pigs following the intravenous infusion of physiological saline solution or histamine solution (2 micrograms/kg/min) for 60 minutes. Total blood flow averaged 2.28 ml/min/gland for control pigs and 4.38 ml/min/gland for histamine-treated pigs (P less than .0005). Mean blood flow to the adrenal glands of histamine-treated pigs (3.15 ml/min/g) was 82% higher than that of control pigs (1.73 ml/min/g); the difference was highly significant (P less than .0005). The result of this study showed that histamine caused an increased blood flow to the porcine adrenal glands.

Effect of peripheral cholinergic activation on the adrenal cortex function

The adrenocortical response to cholinergic agonist and antagonist agents were investigated in intact, hypophysectomized and medullectomized rats. The administration of peripherally active compound neostigmine, was found to cause a significant rise of corticosterone in the intact, and the hypophysectomized animals but not in the medullectomized animals. Meanwhile, the centrally and peripherally active cholinergic agent physostigmine caused a significant rise in the intact, hypophysectomized and medullectomized animals. The results also show that the administration of the ganglionic blocker (e.g. tetraethylammonium or hexamethonium), the muscarinic agonist (pilocarpin) or the muscarinic antagonist (atropin) did not result in any significant changes in corticosterone levels. The results of these experiments might indicate that peripheral cholinergic pathway is involved in the regulation of the adrenal cortex function.