Effect of adrenergic drugs on histamine forming capacity of human leucocytes

Macrophages can produce factors capable of inducing histidine decarboxylase, a histamine-forming enzyme, in vivo in the liver, spleen, and lung of mice

Injection into mice of culture supernatant of P388D1 cells, a murine macrophage cell line, produced a rapid increase in histidine decarboxylase (HDC) activities in the liver, spleen, and lung. Factors in the culture supernatant capable of inducing the HDC elevation were purified by gel filtration and chromatofocusing. Throughout these procedures, the HDC-inducing activity accompanied the mitogenic activity for thymocytes or interleukin 1 (IL-1) activity. Although, because of low purity of the preparations, it is not confirmed whether the HDC inducer is IL-1 itself or not, the present results indicate that P388D1 cells can produce a factor(s) capable of inducing HDC in mouse tissues in vivo. After the injection of the HDC-inducing factor into mice, HDC induction in the tissues occurred within 2 hr and peaked at 2 to 4 hr, resulting in the increase in histamine levels 1 to 10 nmol/g tissue. These results provide important information concerning the source of endogenous histamine that might be involved in inflammatory reactions in delayed-hypersensitivity reactions or in the immune regulation observed in many in vitro systems.

Effect of sympathomimetic amines on the histamine forming capacity of human leucocytes

1 The effects of alpha- and beta-adrenoceptor stimulants on the histamine-forming capacity (HFC) of human isolated leucocytes have been studied, in vitro.2 It was confirmed that antigen significantly stimulates the HFC of human leucocytes.3 beta-Adrenoceptor stimulants, such as isoprenaline and salbutamol (10(-6)-10(-3)M) significantly inhibited the HFC of human leucocytes in the presence and absence of antigen. At concentrations lower than 10(-6)M, this effect was not observed. In general the degree of inhibition of HFC by beta-adrenoceptor stimulants followed their potency as beta-adrenoceptor stimulants.4 alpha-Adrenoceptor stimulants significantly stimulated leucocyte HFC; noradrenaline within a limited concentration of 10(-6)M, while stimulation was seen consistently with phenylephrine at concentrations of 10(-7)-10(-4)M. Adrenaline, which stimulates both alpha- and beta-adrenoceptors, produced small inhibition, no effect, or a degree of stimulation.5 Phentolamine, an alpha-adrenoceptor blocking agent, produced an effect opposite to that of the alpha-adrenoceptor stimulants, i.e. a significant inhibition of the HFC of human isolated leucocytes.

Implication of gastric mucosal histamine in inhibition by isoprenaline of pentagastrin-induced gastric secretion

1 The effect of isoprenaline on pentagastrin-induced gastric secretion was studied in conscious rats with Heidenhain pouches. The influence of isoprenaline on pentagastrin-induced release and formation of gastric mucosal histamine was also examined.2 Isoprenaline strongly inhibited pentagastrin-induced acid secretion, an inhibition which could not be overcome by increasing the dose of pentagastrin.3 Propranolol blocked the inhibitory effect of isoprenaline on pentagastrin-induced acid secretion.4 Isoprenaline enhanced pepsin secretion induced by pentagastrin, an effect which was blocked by propranolol.5 Isoprenaline reduced the increase in formation and release of gastric mucosal histamine following pentagastrin infusion, an inhibitory influence which was almost completely blocked by propranolol.6 The inhibition by isoprenaline of pentagastrin-induced acid secretion is tentatively related to alterations in gastric mucosal histamine occurring simultaneously.

Can the actions of adrenoceptor agonists and antagonists on pentagastrin-induced gastric secretion be due to their effects of histamine formation?

1 The effects of some adrenoceptor agonists and antagonists which have been reported to affect histamine formation in leucocytes (Assem & Feigenbaum, 1972) have been investigated on gastric secretion in conscious dogs with Heidenhain pouches.2 Submaximal secretion in response to pentagastrin was enhanced by propranolol (0.1-1.0 mg/kg i.v.) and phenylephrine (1.0 mug kg(-1) min(-1) i.v. for 20 min), which increase histamine formation, and was decreased by phentolamine (2 mg/kg i.v.) and isoprenaline (0.05-0.2 mug kg(-1) min(-1) i.v. for 30 min), which decrease histamine formation. Practolol (2 mg/kg i.v.), which has no effect on histamine formation, had no effect on secretion.3 Acid secretion in response to histamine was either unaffected or affected in the opposite direction by these drugs.4 The effects of the drugs on pentagastrin-induced secretion were not secondary to changes in mucosal blood flow (radioactive aniline clearance).5 The results are consistent with the hypothesis that acid secretion in response to pentagastrin involves the formation of endogenous histamine.

Enhancement of pentagastrin-induced gastric acid secretion by clonidine in the conscious dog

The effect of intravenous clonidine on pentagastrin-induced gastric acid secretion has been studied in conscious dogs with Heidenhain pouches. Dose-dependent enhancement of secretion was found in response to clonidine (5-20 mu/kg). Clonidine (20 mug/kg) increased the maximal secretory rate to pentagastrin to a value not significantly different from the maximal response to histamine.

Beta-adrenoceptor blocking properties and cardioselectivity of M & B 17,803A

1. The beta-adrenoceptor blocking properties of (+/-)-1-(2-acetyl-4-n-butyramidophenoxy)-2-hydroxy-3-isopropylaminopropane hydrochloride (M&B 17,803A) have been compared with those of practolol and propranolol in the guinea-pig, cat and dog.2. Following either intravenous or oral administration in the cat or dog, M&B 17,803A and practolol had similar potency in antagonizing isoprenaline-induced tachycardia and both showed cardioselectivity, but both were less potent than propranolol.3. M&B 17,803A and practolol had approximately one hundredth the intravenous potency of propranolol in increasing the severity of anaphylactic bronchospasm in the conscious sensitized guinea-pig.4. M&B 17,803A possessed less marked intrinsic sympathomimetic activity than practolol but, like propranolol, it had significant local anaesthetic properties and increased the refractory period of rabbit isolated atria.