MUC7 expression in the human lacrimal gland and conjunctiva.

Purpose: Several mucins including MUC1, MUC2, MUC4, and MUC5AC have been identified at the ocular surface and in tears. The lacrimal gland, however, is not generally considered a source of ocular mucin. Because the lacrimal glands are similar to the salivary glands, we hypothesized that the lacrimal gland would express MUC7, a distinctive salivary mucin.

Characterization of human ocular mucin secretion mediated by 15(S)-HETE.

Purpose: The eicosanoid 15-(S)-hydroxy-5,8,11,13-eicosatetraenoic acid [15(S)-HETE] is reported to stimulate mucin production in both airway and ocular surface epithelia. The current study was undertaken to evaluate the effects of 15(S)-HETE on secretion of specific ocular mucins by human conjunctiva.

Methods: Segments of human bulbar conjunctival tissue were incubated with 15(S)-HETE (1-1000 nM) for 30 minutes at 37 degrees C.

[Presynaptic 5-hydroxytryptamine receptors enhance cholinergic neurosecretion in the human iris-ciliary body].

Objective: To characterize presynaptic 5-hydroxytryptamine (5-HT) heteroreceptors which modulate 3H-acetylcholine (3H-ACh) release in isolated human iris-ciliary bodies (ICBs).

Methods: ICB tissue segments were perfused and incubated with 3H-choline, and electrically stimulated four times (S1, S2, S3 and S4) at 10 Hz for 1 min to elicit 3H-ACh secretion. Test agents, 5-HT agonists and antagonists, were added before S2, S3 and S4 and their effects were determined by the stimulation ratio (Sx/S1) of evoked 3H-ACh release.

Quantification of MUC5AC protein in human tears.

Purpose: MUC5AC has been identified as a major secretory mucin of conjunctival goblet cells and precorneal tear film. However, no method has been reported to quantify MUC5AC protein in human tears. The objective of this study was to establish a method to measure the amount of MUC5AC in human tears and to correlate the amount of MUC5AC with age, gender, and dry eye diseases.

Quantification of MUC2 and MUC5AC transcripts in human conjunctiva.

Purpose: Transcripts of mucins 1, 4, and 5AC have been identified in human conjunctival tissue. Of these, only MUC5AC has been localized to goblet cells. MUC2 is a goblet cell mucin originally identified in the intestinal mucosa.

MUC5AC mucin is a component of the human precorneal tear film.

Purpose: Mucins are important structural and functional components of the precorneal tear film, yet little is known of their composition and synthesis. The mRNAs of MUC1, MUC4, and MUC5AC have previously been identified in human conjunctiva. Of these, only MUC5AC mRNA appears to be associated with goblet cells.

Regulation of ocular mucin secretion by P2Y2 nucleotide receptors in rabbit and human conjunctiva.

The effects of adenine analogues on secretion of high molecular weight, mucin-like glycoproteins (mucins) by conjunctival goblet cells were investigated using isolated rabbit and human conjunctiva. Mucin secretion was assayed using a quantitative dot-blot assay of Helix pomatia agglutinin-horseradish peroxidase binding to mucins absorbed to nitrocellulose filters. In rabbit conjunctiva, exogenous ATP (10(-7)-10(-3) m) induced a concentration-dependent, four-fold increase in mucin secretion that reached a plateau 15 min after drug addition.

M2-type muscarinic receptors mediate prejunctional inhibition of norepinephrine release in the human iris-ciliary body.

Human muscarinic receptors comprise a family of five separate gene products, three of which (designated as M1, M2 and M3 subtypes) can be distinguished pharmacologically. Previous work indicates that sympathetic nerve terminals in the anterior uvea contain prejunctional muscarinic receptors that, upon activation by agonists, inhibit the neural release of norepinephrine. The aim of this study was to characterize the prejunctional effects of muscarinic agents on the electrically-evoked secretion of 3H-norepinephrine in isolated, superfused human iris-ciliary body tissue segments.

Prejunctional alpha 2-adrenoceptors and adenylyl cyclase regulation in the rabbit iris-ciliary body.

Agents that elevate intracellular cyclic AMP (cAMP) have been found to enhance the synaptic discharge of norepinephrine (NE) from sympathetic nerve terminals in the rabbit iris-ciliary body and other peripheral tissues. We explored the hypothesis that prejunctional alpha 2-adrenergic receptors that mediate feedback inhibition of NE release may be coupled to adenylyl cyclase inhibition. To indirectly monitor cAMP changes in sympathetic axon terminals, we analyzed the cAMP-mediated activation of tyrosine hydroxylase, a sympathetic marker protein that undergoes acute phosphorylation and activation by cAMP-dependent protein kinase A.

Neuromodulatory effect of sulprostone on the circadian elevation of intraocular pressure in rabbits.

Topical application of sulprostone, a preferential prostaglandin EP3 receptor agonist, caused a dose-dependent reduction of the circadian elevation of intraocular pressure (IOP) in New Zealand albino rabbits which were entrained to 12-hr/12-hr light-dark environment. Corresponding to the effect on IOP, 0.2 micrograms, 2 micrograms, and 20 micrograms sulprostone decreased the norepinephrine (NE) concentration in the aqueous humor in the dark phase.

Prejunctional receptors and second messengers for angiotensin II in the rabbit iris-ciliary body.

Angiotensin II has been shown to act prejunctionally to facilitate sympathetic neutrotransmission in various tissues including the iris-ciliary body. In the present study, we characterized the prejunctional angiotensin II receptor subtype and its signal transduction pathway in the rabbit iris-ciliary body. Angiotensin II caused concentration-dependent facilitation of electrically evoked [3H]-norepinephrine overflow from the isolated, superfused rabbit iris-ciliary body without affecting basal tritium efflux.

Prejunctional modulation of norepinephrine release in the human iris-ciliary body.

Purpose: To characterize the prejunctional mechanisms that control the impulse-evoked release of norepinephrine in the isolated, superfused human iris-ciliary body.

Methods: Human iris-ciliary body tissue segments were preincubated with 3H-norepinephrine, superfused and electrically-stimulated in vitro to evoke the discharge of 3H-norepinephrine. The effects of prejunctional modulators on evoked 3H-norepinephrine overflow were evaluated.

Prejunctional prostaglandin receptors in the human iris-ciliary body.

Prostaglandins (PGs) of the E series have been shown to modulate sympathetic neurotransmitter release in a variety of peripheral tissues and organs, including the eye. In this study, we evaluated the inhibitory effects of a series of naturally-occurring and synthetic PGs on field stimulation-evoked release of 3H-norepinephrine (3H-NE) from isolated, superfused segments of human iris-ciliary body. Field-stimulated 3H-NE secretion was calcium-dependent, blocked by selective inhibitors of voltage-sensitive calcium and sodium channels, and originated from a desipramine-sensitive transmitter pool.

Prejunctional inhibitory effects of prostanoids on sympathetic neurotransmission in the rabbit iris-ciliary body.

Both naturally occurring and synthetic prostaglandins (PGs) caused concentration-dependent inhibition of electrically evoked [3H]norepinephrine (NE) overflow from the isolated, superfused rabbit iris-ciliary body without affecting basal tritium efflux. The rank order of potencies of the agonists was: sulprostone greater than 16, 16-dimethyl-PGE2 greater than PGE2 greater than 11-deoxy-PGE1 greater than iloprost (stable PGl2 analog) greater than PGF2 alpha greater than or equal to PGD2. However, the Tx-mimetic, U-46619, was without effect on transmitter release at concentrations up to 1 microM.

Muscarinic cholinergic inhibition of adenylate cyclase in the rabbit iris-ciliary body and ciliary epithelium.

The effects of cholinergic agents on hormone-stimulated cyclic AMP (cAMP) accumulation were investigated in iris-ciliary body segments, excised ciliary processes, and isolated ciliary epithelium from albino rabbit eyes. In all three tissue preparations, the cholinergic agonist carbamylcholine markedly inhibited the stimulation of cAMP biosynthesis by vasoactive intestinal peptide VIP--a potent activator of nonpigmented ciliary epithelial adenylate cyclase. Carbamylcholine also attenuated cAMP increases mediated by isoproterenol, prostaglandin E2, and forskolin.

Inhibitory effects of neuropeptide Y on sympathetic neurotransmission in the rabbit iris-ciliary body.

Neuropeptide Y (NPY, 1-300 nM) mediated a concentration-dependent inhibition of field stimulation-evoked [3H]norepinephrine (NE) overflow from the isolated, superfused rabbit iris-ciliary body. At equimolar concentrations (100 nM), the homologous neuropeptide peptide YY (PYY) mimicked the effects of NPY, whereas pancreatic polypeptide (PP) and the C-terminal fragment of NPY did not modify [3H]NE release. NPY-induced inhibition of [3H]NE release was unaffected by pretreatment of tissues with atropine (100 nM) plus yohimbine (100 nM) and was non-additive with the maximal prejunctional effects of carbamycholine or clonidine, indicating that NPY acts independently of prejunctional muscarinic or alpha 2-adrenergic receptor activity to reduce [3H]NE overflow.

Potentiation of norepinephrine secretion by angiotensin II in the isolate rabbit iris-ciliary body.

The prejunctional effects of angiotensin II (AII) on stimulation-evoked secretion of 3H-norepinephrine (3H-NE) were investigated by in vitro methods in isolated, superfused rabbit iris-ciliary body preparations. AII (0.1-10 nM) concentration-dependently enhanced the field- stimulated release of 3H-NE (EC50 = 0.

Benzodiazepine binding sites on PC12 cells: modulation by nerve growth factor and forskolin.

PC12 pheochromocytoma cells show increased binding of the peripheral type benzodiazepine Ro 5-4864 after treatment with nerve growth factor (NGF) in membrane preparations. Forskolin, an activator of adenylate cyclase, acts synergistically with NGF to produce further increases in binding, but by itself produces no effect. The increased binding appears to reflect increases in receptor number, since Kd remains unchanged.

Effects of calcium channel antagonists on the depolarization-evoked release of norepinephrine in the rabbit iris-ciliary body.

The effects of several representative calcium channel antagonists on depolarization-evoked release of [3H]-norepinephrine were investigated in isolated, superfused rabbit iris-ciliary bodies. Potassium (50 mM)-evoked neurosecretion was blocked by 5 mM CoCl2 and partially inhibited by 10(-6) M nitrendipine or verapamil. Electrically-evoked neurosecretion was similarly blocked by CoCl2, but was unaffected by nitrendipine or verapamil.

Cholinergic inhibition of adrenergic neurosecretion in the rabbit iris-ciliary body.

The prejunctional effects of cholinergic agents on release of norepinephrine from sympathetic nerve endings were investigated in the isolated, superfused rabbit iris-ciliary body. Stimulation-evoked release of 3H-norepinephrine was inhibited by the cholinergic agonists methacholine, oxotremorine, muscarine, carbamylcholine and acetylcholine (plus eserine), but was unmodified by pilocarpine or nicotine. Agonist-induced inhibition was antagonized selectively by atropine, indicating a muscarinic response.

Alpha-2 adrenergic modulation of norepinephrine secretion in the perfused rabbit iris-ciliary body.

Clonidine and other selective alpha-2 adrenergic agonists have been found to lower intraocular pressure in the eyes of rabbits and primates, including humans. It has been suggested that the ocular hypotensive response to alpha-2 agonists may be mediated, in part, by prejunctional inhibition of norepinephrine secretion at intraocular synapses. In this study, we have investigated the effects of adrenergic agonists and antagonists on field-stimulated, Ca++-dependent release of 3H-norepinephrine (3H-NE) from isolated, perfused rabbit iris-ciliary bodies and have utilized radioligand binding methods to identify prejunctional adrenoceptors in this tissue.