Histamine elevates the intracellular cyclic AMP levels in cultured embryonic chick retinal pigment epithelium. The half-maximal activity is 6 X 10(-6) M. The effect of histamine is mediated by H2 receptors, i.e., inhibited by the H2 antagonist cimetidine and not affected by the H1 antagonists diphenhydramine and pyrilamine. The inhibition constant (KI) of cimetidine is 1.3 X 10(-8) M. Thus, the...

Activation of alpha 1-adrenergic receptors in BC3H-1 muscle cells has been shown previously to mobilize intracellular Ca2+, which can be monitored as enhanced 45Ca2+ unidirectional efflux. We report here that histamine also stimulates 45Ca2+ efflux in these cells (Kact = 5.50 microM, nH = 0.94 +/- 0.04), reflecting mobilization of intracellular Ca2+ from a source similar to that accessed by alp...

Nerve growth factor (NGF) as an autocrine or paracrine growth factor plays a critical role in the pathogenesis and progression of human pancreatic cancer. NGF is synthesized as a proform (proNGF) that, when cleaved, releases mature ligand (mNGF). proNGF and mNGF bind to high-affinity tyrosine kinase receptor A (TrkA) and low-affinity receptor p75 to different extents. Histamine is a potent stim...

A univalent and bioactive fluorescent derivative of histamine bound to the surface of human polymorphonuclear leukocytes; free histamine was found to compete with this derivative for binding sites. Histamine H2-receptor specificity was indicated by binding inhibition experiments using cimetidine (H2-specific) but not diphenhydramine (H1-specific). Video-intensification fluorescence microscopy w...

Histamine causes vasodilation in the dog by activation of H1 and H2 receptors blocked by mepyramine and metiamide, respectively. Experiments were conducted in anesthetized dogs to determine the participation of H1 and H2 receptors in several forms of physiological dilatation. Mepyramine attenuated both histamine-induced and active-reflex dilatation in the hindlimb. Metiamide caused a further re...

The role of histamine H1 and H2 receptors in the lung is not clear. H1 receptor blockade results in bronchodilatation and inhibition of histamine induced bronchoconstriction. H2 receptor blockade in vitro prevents the normal negative feedback of histamine on further mediator release in antigen challenge. Bronchospasm in guinea pigs given antigen challenge is enhanced by previous administration ...

Ventilation oscillates throughout a day in parallel with oscillations in metabolic rate. Histamine affects ventilation and the balance of the energy metabolism via H1 receptors in the brain. We tested the hypothesis that the ventilatory response to hypoxia varies between light and dark periods and that histamine H1 receptors are required for the circadian variation, using wild-type (WT) and his...

Histamine is an accepted neurotransmitter and/or neuromodulator in the central nervous system (CNS). Its neuronal system in the brain is well organized, with cell bodies localized in a small area of the posterior hypothalamus. Diverse biological actions of histamine are mediated via three classes of receptors termed H1, H2, and H3. The existence of other histamine receptor subtypes is likely in...

Previous reports demonstrated that the expression of thrombomodulin (TM) in endothelial cells was modulated by various agents. Although TM was down-regulated by endotoxin or cytokines, up-regulation of TM was accomplished when endothelial cells were stimulated with unphysiologically high concentrations of cyclic AMP derivatives or tumour-promoting phorbol esters. We investigated the expression ...

The effect of histamine on bovine isolated retinal small arteries (internal diameter, approximately 240 microns) was studied. Histamine induced a concentration-dependent relaxation in 43 of 53 vessels. The histamine-induced relaxation involves primarily activation of H1-receptors, with H2-receptors also affected as evidenced by the effect of selective histamine-receptor agonists and antagonists...