Cyclooxygenase-2 expression in the eyes of cats with and without uveitis

OBJECTIVE To characterize the distribution and intensity of cyclooxygenase (COX)-2 expression in the eyes of cats with and without uveitis and to determine whether COX-2 expression is correlated with severity of inflammation. SAMPLES Archived ocular tissue specimens from 51 cats with and 10 cats without ocular disease. PROCEDURES Specimens from only 1 eye were evaluated for each cat. Specimens were stained with H&E stain or immunohistochemical stain for detection of COX-2 and reviewed. For each eye, the type, severity, and distribution of inflammation and the distribution and intensity of COX-2 expression were determined for the uvea and other ocular tissues. Correlation between COX-2 expression and inflammation severity was also assessed. RESULTS COX-2 was not expressed in any nondiseased eye. Of the 51 diseased eyes, 20 had histologic evidence of lymphocytic-plasmacytic uveitis, 13 had neutrophilic uveitis, 11 had diffuse iris melanoma with uveitis, and 7 had diffuse iris melanoma without uveitis. Of the 44 eyes with uveitis, COX-2 was detected in the uvea of 16, including 11 eyes with lymphocytic-plasmacytic uveitis, 4 with neutrophilic uveitis, and 1 with diffuse iris melanoma-induced uveitis. Inflammation was severe, moderate, or mild in 10, 5, and 1 of those eyes, respectively. Cyclooxygenase-2 was detected in the cornea of 21 eyes with uveitis and 1 eye with diffuse iris melanoma without uveitis. Uveitis severity was positively correlated with COX-2 expression in both the uvea and cornea. CONCLUSIONS AND CLINICAL RELEVANCE Results suggested that COX-2 is an inflammatory mediator in feline uveitis but not diffuse iris melanoma.

Angiotensin converting anzyme (ACE) activity in porcine ocular tissue: effects of diet and ACE inhibitors

The aim of the present experiments was to determine angiotensin converting enzyme (ACE) activity in different parts of the porcine eye, and to examine whether an atherogenic diet influenced ACE activity. Female mini-pigs were fed a standard diet or a diet with high cholesterol to produce atherosclerosis. The animals were killed by an overdose of pentobarbital, and the eyes were enucleated and dissected into iris, ciliary body, retina, and choroid. Crude tissue homogenates were used for determination of ACE activity, which was done with a radioenzymatic assay. In pigs fed a normal diet, basal ACE activity was 18.1 +/- 1.6, 13.6 +/- 1.9, 4.4 +/- 0.6, and 44.7 +/- 8.5 units/mg for iris, ciliary body, retina, and choroid, respectively. The ACE activities in ocular tissues from the pigs that had been fed an atherogenic diet were not significantly different. Nor was the ACE activity in the abdominal aorta and serum significantly different between the two groups. In both groups, the ACE inhibitors captopril and enalaprilat, caused a significant inhibition of the ACE activity in the choroid and ciliary body, with enalaprilat being more potent. In the retina, ACE activity was inhibited significantly only in the group fed a normal diet, whereas ACE activity in the iris was not significantly inhibited in either group. We did not find any differences in ACE activity between pigs fed a normal diet and pigs fed an atherogenic diet, which is in disagreement with previous studies that showed an increased ACE activity in aorta from atherosclerotic mini-pigs. The reason for this discrepancy is not clear, but lower cholesterol levels are one possibility.

Increased matrix metalloproteinases 1, 2, and 3 in the monkey uveoscleral outflow pathway after topical prostaglandin F(2 alpha)-isopropyl ester treatment

OBJECTIVE

To investigate the effects of topical prostaglandin F(2 alpha)--isopropyl ester (PGF(2 alpha)-IE) administration on immunoreactivity of matrix metalloproteinases (MMPs) 1, 2, and 3 within the anterior segment tissues of monkey eyes.

METHODS

Eight eyes from 4 cynomolgus monkeys were evaluated. One eye from each monkey was treated with 2 mg of PGF(2 alpha)-IE twice daily for 5 days, and intraocular pressure reduction was measured. After fixation and processing, deparaffinized sections of anterior segments were immunostained using antibodies to MMP-1 (interstitial collagenase), MMP-2 (gelatinase A), or MMP-3 (stromelysin-1). Optical density along 2 line segments overlying the iris root, ciliary muscle, and adjacent sclera and perpendicular to their long axes was measured using imaging densitometry.

RESULTS

Compared with the contralateral vehicle-treated eyes, statistically significant increases in optical density scores were observed in the iris root, ciliary muscle, and adjacent sclera for all 3 MMPs (P<.01). In these tissues, MMP-1 immunoreactivity was increased by a mean +/- SD of 89% +/- 16%, 61% +/- 8%, and 66% +/- 57%, respectively; MMP-2 immunoreactivity by 129% +/- 53%, 82% +/- 27%, and 267% +/- 210%, respectively; and MMP-3 immunoreactivity by 207% +/- 84%, 83% +/- 49%, and 726% +/- 500%, respectively.

CONCLUSIONS

Treatment of monkey eyes with PGF(2 alpha)-IE induces elevation of MMP-1, MMP-2, and MMP-3 in tissues of the uveoscleral outflow pathway. These increases suggest that MMPs might play an important role in the increased uveoscleral outflow observed with topical prostaglandin treatment.

CLINICAL RELEVANCE

Immunoreactivity of MMPs in tissues of the monkey uveoscleral outflow pathway is increased after topical treatment with PGF(2 alpha)-IE. This response also might be involved in the intraocular pressure--lowering effect of other prostanoids used to treat glaucoma.

Peroxiredoxin in bovine ocular tissues: immunohistochemical localization and in situ hybridization

Peroxiredoxins are widely distributed in nature and constitute a molecular family of antioxidant enzymes which decompose hydrogen peroxide and alkyl hydroperoxides. We have previously characterized a peroxiredoxin from bovine ciliary body and deduced its amino acid sequence from analysis of cDNA clones encoding the protein. In this work, we investigated the immunolocalization of this novel antioxidant enzyme and its mRNA expression in bovine eye tissues. High levels of immunoreactivity and mRNA for the enzyme were detected in corneal epithelium. Distinct immunoreactivity and mRNA expression for peroxiredoxin were also detected in uveal tissues, some of the retinal cell layers and ocular vasculature.

Occurrence of cholinergic nerve fibers in the human uveoscleral tissue

We have studied the cholinergic nerve fibers (CNF) of human uveoscleral tissue in normal and pathological conditions (intraocular pressure: (IOP) of various degrees ) and have performed a quantitative image analysis of CNF with the aim of studying an hypothetical association between IOP and the uveoscleral level of cholinergic neurotransmitter in nerve fiber of the enucleated human eyes. Eleven patients, previously enrolled in our medical protocols are affected by an increase of IOP of various degrees, were subjected to surgical enucleation of one eyeball for traumatic or neoplastic reasons and were the donors of samples of the uveoscleral tissue for CNF demonstration. The samples were also submitted to quantitative image analysis. An enzymatic activity, Acetylcholinesterase (AChe), is present in nerve fibers that innervate the human uveoscleral tissue. The AChe-positive nerve fibers represent about 7.2% of the observed area in normal conditions, while in patients with elevated IOP AChe activity is about 20.3% of the total observed area. The increase of AChe activity in our experiments, all performed under the same conditions, and therefore, with comparable results, may be related with the increase of IOP.

Adrenomedullin and ocular inflammation in the rabbit

Adrenomedullin administered peripherally in the rabbit (at doses of 1.25, 2.5 and 5 microg/kg ) caused a dose-dependent conjunctival hyperemia accompanied by an increase of inflammatory cell number and prostaglandin E(2) concentration in the aqueous humor, and of uveal vascular response and myeloperoxidase activity. The inflammatory effect of the peptide, injected at the dose of 5 microg/kg, was abolished by pretreatment with the inhibitor of nitric oxide synthase, N(G)-nitro-L-arginine methylester (50 mg/kg, i.v.). Moreover, the i.v. pretreatment with the calcitonin gene-related peptide 8-37 fragment (calcitonin gene-related peptide, CGRP-(8-37), 2.5 microg/kg), receptor antagonist of CGRP, did not inhibit the conjunctival hyperemia. In contrast, the i.v. pretreatment with the adrenomedullin receptor antagonist, adrenomedullin-(22-52) fragment (2.5 microg/kg), abolished adrenomedullin-induced ocular inflammation. These results suggest that adrenomedullin causes conjunctival hyperemia, and this effect involves the nitric oxide system acting through specific adrenomedullin receptors.

Uveoscleral outflow in dog's eye: role of several enzymes

The morphological pattern of several enzymes (succinic dehydrogenase--SDH, glucose-6-phosphate dehydrogenase--G6PDH and lactic dehydrogenase--LDH) was evaluated in normal dog eyes. Special attention was paid to the uveo-scleral tissue. Cryostatic sections of dog eye were stained with toluidine blue for the recognition of the microanatomical details or with histoenzymatic methods for SDH, G6PDH and LDH activities using sodium succinate, glucose-6-phosphate and sodium lactate as substrates respectively, nicotinamide adenine dinucleotide (NAD) as a reducing agent and sodium nitro-blue-tetrazolium as a colouring substance. A moderate positive reaction for SDH and a strong positive reaction for LDH were observed in the uveoscleral tissue, while G6PDH gave negative staining. Some considerations regarding a possible active role of these enzymatic activities to the aqueous humor outflow are suggested.

Mast cell heterogeneity in the human uvea

To identify chymase- and tryptase-positive mast cells in the human uvea, and to study their associations with different types of resident uveal cells, uveal specimens from 24 human donor eyes were cryosectioned in sagittal and tangential planes. Enzyme histochemical staining of chymase was combined with immunohistochemical staining for tryptase, detected with the APAAP method. Fluorescence immunohistochemistry was performed with antibodies against c-kit, alpha smooth muscle actin, protein gene product (PGP) 9.5, CD45, and HLA-DR. In different uveal compartments, the total amounts of mast cells were calculated and the distributions of chymase and tryptase were quantified. All uveal mast cells were c-kit and CD45 positive and HLA-DR negative. No association existed between mast cells and actin-containing cells. Only a few mast cells were in close association with PGP 9.5-labeled nerve fibers. In the choroid, most mast cells were located in the inner central part (mean density = 48.9/mm(2)), and contained both chymase and tryptase (96%). The ciliary muscle contained numerous mast cells (mean density = 33.7/mm(2)), many of them tryptase positive but chymase negative (63%). In the pars plana, a high number of chymase-positive, tryptase-negative mast cells were found (20%). In the iris only a few mast cells were present. Although the choroid contains the most common subtype of mast cells, a unique situation concerning the distribution of chymase and tryptase is present in the anterior uveal tissues. A possible role for these cells in the special immunological situation of the anterior eye chamber merits further investigation.

Carbonic anhydrase inhibitors: synthesis of water-soluble, topically effective intraocular pressure lowering aromatic/heterocyclic sulfonamides containing 8-quinoline-sulfonyl moieties: is the tail more important than the ring?

Reaction of 20 aromatic/heterocyclic sulfonamides containing a free amino, imino, hydrazino or hydroxyl group, with 8-quinoline-sulfonyl chloride afforded a series of water-soluble (as hydrochloride or triflate salts) compounds. The new derivatives were assayed as inhibitors of the zinc enzyme carbonic anhydrase (CA), and more precisely of three of its isozymes, CA I, II (cytosolic forms) and IV (membrane-bound form), involved in important physiological processes. Efficient inhibition was observed against all three isozymes, but especially against CA II (in nanomolar range), which is the isozyme known to play a critical role in aqueous humor secretion within the ciliary processes of the eye. Some of the best inhibitors synthesized were topically applied as 2% water solutions onto the eye of normotensive and glaucomatous albino rabbits, when strong and long-lasting intraocular pressure (IOP) lowering was observed with many of them. This result prompted us to reanalyze the synthetic work done by other groups for the design of water soluble, topically effective antiglaucoma sulfonamides. According to these researchers, the IOP lowering effect is due to the intrinsic nature of the specific heterocyclic sulfonamide considered, among which the thienothiopyran-2-sulfonamide derivatives represent the best studied case. Indeed, the first agents developed for such applications, such as dorzolamide, are derivatives of this ring system. In order to prove that the tail (in this case the 8-quinoline-sulfonyl moiety) conferring water solubility to a sulfonamide CA inhibitor is more important than the ring to which the sulfonamido group is grafted, we also prepared a dorzolamide derivative to which the 8-quinoline-sulfonyl moiety was attached. This new compound is quite water soluble as hydrochloride salt, behaves as a strong CA II inhibitor, and fared better than the parent molecule in lowering IOP in experimental animals. Thus, the tail conferring water solubility to such an enzyme inhibitor is more important for its topical activity as antiglaucoma drug than the heterocyclic/aromatic ring to which the sulfonamido moiety is grafted.

Matrix metalloproteinase-1 localization in the normal human uveoscleral outflow pathway

PURPOSE

To determine the distribution of matrix metalloproteinase-1 (MMP-1) in the uveoscleral outflow pathway and other anterior segment tissues of normal human eyes.

METHODS

Normal human eyes were fixed in methacarn and sectioned and immunostained using a specific polyclonal antibody to MMP-1. Immunoreactivity was visualized using diaminobenzidine. To compare the staining intensity in various tissues, the mean optical density within the ciliary body, mid-iris stroma, iris root, uveal trabecular meshwork, cornea, and sclera was determined using imaging densitometry. To determine the cellular distribution of MMP-1 in ciliary muscle, additional sections were double-immunostained using antibodies to MMP-1 and calponin. These sections were examined by confocal laser scanning microscopy. Specificity of the antibody to MMP-1 in ocular tissues was confirmed by western blot analysis with uveal tract homogenates.

RESULTS

Moderate-to-strong MMP-1 immunoreactivity was observed in ciliary muscle, iris, sclera, corneal endothelium, and ciliary nonpigmented epithelium. Lighter immunoreactivity was observed in corneal epithelium, blood vessels, trabecular meshwork, Schlemm's canal, and associated collector channels. Confocal microscopy showed that ciliary muscle MMP-1 was primarily inside ciliary muscle cells. Densitometry showed that net optical density was approximately fivefold greater in ciliary muscle, iris root, and sclera than in trabecular meshwork.

CONCLUSIONS

MMP-1 was prominently identified in regions of the anterior segment of normal human eyes associated with the uveoscleral outflow pathway and in the iris, corneal endothelium, and ciliary nonpigmented epithelium. These data support the hypothesis that MMP-1 activity is involved in regulating uveoscleral outflow facility.

Distribution of thioltransferase (glutaredoxin) in ocular tissues

PURPOSE

A new redox regulating enzyme, thioltransferase (TTase), has been found in the lens. The authors investigated whether TTase is also present in other ocular tissues.

METHODS

Fresh enucleated bovine eyes were obtained from a local abattoir 4 hours after death. The eyes were processed immediately to remove corneal epithelial cells, conjunctiva, corneal endothelial cells, iris, ciliary body, lens epithelial cells, vitreous body, and retina. Other than conjunctiva and vitreous body, which were collected from a single eye, all other tissues were pooled from three bovine eyes. Each sample was homogenized in 0.1 M phosphate buffer, pH 7.4, and centrifuged at 10,000 g for 20 minutes, and the supernatant was assayed for TTase activity. Total RNA from each tissue sample was extracted and used for slot blot hybridization using cDNA from pig liver TTase with beta-actin as control.

RESULTS

Among all the ocular tissues tested, iris showed the highest TTase activity (35 mU/mg protein) followed by conjunctiva, corneal epithelial cells, and corneal endothelial cells. Ciliary body, lens epithelial cells, and retina had moderate activity. No activity could be detected in vitreous body. The presence of this enzyme transcript in these ocular tissues was further confirmed by the positive slot blot hybridization with the pig liver TTase cDNA. Here again, iris showed the highest TTase mRNA expression, followed by ciliary body, lens epithelial cells, corneal endothelial cells, conjunctiva, retina, and corneal epithelial cells. The whole lens showed the lowest TTase mRNA expression, and no TTase mRNA was found in the vitreous body.

CONCLUSIONS

TTase was found in most ocular tissues and was concentrated in the anterior segment of the eye. Highest activity was found in the iris, conjunctiva, corneal epithelial, and endothelial cells. TTase was absent in the vitreous body.

Induction of rabbit cyclooxygenase 2 in the anterior uvea following glaucoma filtration surgery

PURPOSE

This study was undertaken to evaluate for the presence of cyclooxygenase 2 (COX2) gene expression in the anterior uvea of rabbits following glaucoma filtration surgery.

METHODS

One of the following surgical procedures were performed on the right eye of New Zealand white albino rabbits: (1) paracentesis (2.5 mm limbal incision); (2) iridectomy through a 2.5 mm limbal incision; (3) lamellar scleral flap formation or (4) full glaucoma filtration surgery. The animals were sacrificed within 3 hours of post-surgery, and the anterior uveal tissues were isolated. Polymerase chain reaction-based techniques were employed to assay for the presence of COX2 transcript.

RESULTS

A partial coding sequence of the previously unreported rabbit COX2 gene was obtained. COX2 mRNA was detected in the operated eyes of animals that underwent either full filtration surgery or iridectomy through a limbal incision.

CONCLUSIONS

In normal rabbit anterior uveal tissue, there appears to be minimal expression of COX2 message. After experimental glaucoma filtration surgery, there is rapid induction of COX2 message.

Hydroxyindole-O-methyltransferase activity in ocular and brain structures of rabbit and hen

Relative activities of hydroxyindole-O-methyltransferase (HIOMT) of some brain and ocular structures of the rabbit and hen were analyzed using different 5-hydroxyindoles, i.e., N-acetylserotonin (NAS), 5-hydroxytryptophol (HTOL), 5-hydroxytryptophan (HTP), 5-hydroxytryptamine (HT), and 5-hydroxy-3-indoleacetic acid (HIAA), as enzyme substrates. Pineal glands of both species, as well as hen retina, are capable of producing, to varying degrees, melatonin, 5-methoxytryptophol, and 5-methoxytryptamine. Hen choroid and iris-ciliary body O-methylated NAS and HTOL, whereas rabbit choroid and, to a much lesser extent, hypothalamus and cerebral cortex all O-methylated only NAS. No measurable HIOMT activity was found in hen brain. NAS was a preferred substrate for HIOMT in the hen tissues, whereas in the rabbit pineal gland NAS and HTOL were equally good substrates for HIOMT. Other tested 5-hydroxyindoles, i.e., HTP, HT, and HIAA, were poor methyl acceptors. Of the tissues examined, the highest HIOMT activity was found in the hen pineal gland, followed by the rabbit pineal gland and hen retina. No significant differences between day and nighttime enzyme activities were observed in the pineal gland and retina of either species. The data suggest that in vertebrates some nervous and ocular tissues possess the potential to produce 5-methoxyindole compounds; however, the HIOMT-catalyzed process shows remarkable substrate-, tissue- and species-dependent variations.

Indoleamine 2,3-dioxygenase activity in the aqueous humor, iris/ciliary body, and retina of the bovine eye

The enzyme indoleamine 2,3-dioxygenase (IDO), which uses free oxygen radicals to cleave the pyrrole ring of indoleamines and give kynurenamines, has previously been found in most tissues, but not in the eye. In this study, IDO activity was measured in post-mortem bovine eyes using Yamazaki's method with L-tryptophan as substrate. Because of the physiological importance of IDO in the protection against free oxygen radical damage, a search was conducted to find this enzyme in the eye. Products of tryptophan degradation by IDO, the kynurenine and 3-hydroxyanthranilic acid were detected and measured in the aqueous humor, iris/ciliary body, and the retina by high-performance liquid chromatography (HPLC) coupled with electrochemical detection. IDO activity was 3.2, 9.0 and 10 nmol/mg protein per h for the aqueous humor, iris/ciliary body, and retina, respectively. These findings suggest that, because of its scavenger properties, IDO is involved in the protection of the eye where, because of its transparency, free radicals are formed not only in the normal oxidation process, but also photochemically.

NADPH diaphorase localization and nitric oxide synthetase activity in the retina and anterior uvea of the rabbit eye

The distribution of the enzyme nicotinamide adenine dinucleotide phosphate (NADPH) diaphorase was examined histochemically in the retina, iris, ciliary processes, cornea and conjunctiva of the rabbit eye. The epithelial cells of the ciliary process, iris, conjunctiva and, to a lesser extent, the cornea all showed intense staining. In the retina, staining for NADPH diaphorase was intense in the inner segments of the photoreceptors and a sparsely distributed population of amacrine cells. In addition, another population of amacrine cells, some presumed ganglion cells as well as a number of horizontal cells, stained less intensely for the enzyme. The retina, ciliary processes and, as a comparison, the cerebellum of the rabbit all contain nitric oxide synthetase (NOS) activity, as each tissue can metabolize citrulline from arginine. This process is Ca2+ dependent and is reduced by the NOS inhibitor, NG-monomethyl-L-arginine. The presence of NOS activity in the ciliary processes and the localization of NADPH diaphorase in the ciliary epithelial cells are of significance as they suggest that the ciliary epithelial cells may contain NOS which would imply a role for nitric oxide in aqueous humour production.

Nerve fibers showing immunoreactivities for thyrosine hydroxylase and dopamine-beta-hydroxylase re-appear in the guinea pig uvea after sympathectomy

After sympathectomy we have studied the re-appearance of nerve fibers showing catecholaminergic characteristics in the uvea of the guinea pig. Immunoreactivities for two catecholamine symthetizing enzymes, tyrosine hydroxylase (TH) and dopamine-beta-hydroxylase (DBH), were used as markers. Both TH-like and DBH-like immunoreactive nerve fibers disappeared after the extirpation of ipsilateral superior cervical ganglion. In the choroid the TH-like and DBH-like immunoreactive nerve fibers re-appeared within 2 weeks. In the iris and the ciliary body both of these types of immunoreactive nerve fibers re-appeared 10 weeks after the denervation. The morphological appearance of these re-appearing nerve fibers was not similar to those in the non-denervated uvea.

Cyclo-oxygenase and lipoxygenase pathways in cynomolgus and rhesus monkey conjunctiva, anterior uvea and eyelids

The capacity of cynomolgus and rhesus monkey conjunctiva, anterior uvea and eyelids to synthesize cyclo-oxygenase and lipoxygenase products from arachidonic acid was assessed. Both conjunctiva and eyelid tissues of cynomolgus and rhesus monkeys synthesized detectable amounts of cyclo-oxygenase and lipoxygenase products, indicating the presence of cyclo-oxygenase and 5- and 12-lipoxygenase activities in these tissues. In comparison, cynomolgus anterior uvea synthesized a considerably lesser amount of cyclo-oxygenase products. The cyclo-oxygenase activity was considerably greater than the lipoxygenase activity in cynomolgus and rhesus conjunctiva and eyelids.

Tyrosinase activity in the uveal tissue of the adult bovine eye

Tyrosinase activity in crude extracts from various tissues of the adult bovine eye was examined biochemically. Enzyme activity was measured by using L-3,4-dihydroxyphenylalanine (L-DOPA) as substrate and determining colorimetrically by an increase in absorbancy at 400 or 475 nm. Tyrosinase activity was found in the ciliary body, iris, and choroid with the ciliary body having the highest enzyme activity. The enzyme was 1324-fold purified from the crude extract of the ciliary body by ammonium sulfate fractionation, trypsin digestion, followed by chromatography on Sephacryl S-200, hydroxylapatite, and DEAE-cellulose columns. The apparent Km value for L-DOPA was 0.2 mM and the molecular weight of the enzyme was estimated to be 70000 by gel method. The enzyme activity was markedly reduced by phenylthiourea and diethyldithiocarbamate, specific inhibitors of tyrosinase.

The synthesis of cyclooxygenase products in ocular tissues of various species

In the present study we compared the synthesis of various cyclooxygenase products in albino rabbit, dog (puppy and adult), cat, cow and human ocular tissues from 14C-arachidonic acid (AA). Albino rabbit conjunctiva synthesized a substantial amount (47%) of cyclooxygenase products, while cat and dog (puppy as well as adult) conjunctival tissues synthesized lesser but significant amounts of cyclooxygenase products from 14C-AA. Cyclooxygenase activity in the anterior uvea of different species tested was in the following order of potency: cat greater than albino rabbit greater than dog greater than human greater than cow. Furthermore, human and cow anterior uvea synthesized significantly lesser amount of cyclooxygenase products from 14C-AA than amounts from an intermediate substrate, 14C-PGH2. Interestingly, cow anterior uvea synthesized PGF2 alpha and 6-keto-PGF1 alpha (a stable metabolite of PGI2) while human anterior uvea synthesized all cyclooxygenase products from 14-C-PGH2.

Carbonic anhydrase distribution in the human and monkey eye by light and electron microscopy

The distribution of carbonic anhydrase (CA) in the eye of man and three species of monkeys was studied by light and electron microscopy using the histochemical method of Hansson. Carbonic anhydrase staining was found in the corneal endothelium. In monkeys the endothelial cells covering the inner surface of the operculum were also stained, whereas in the human the staining stopped at Schwalbe's line. In the trabecular meshwork no cells exhibited CA staining. The iris dilator muscle showed some staining, while no clear staining was found in the pigment epithelium (PE). In the ciliary body both the PE and the non-pigmented epithelium (NPE) displayed CA staining, most prominently in the basal and lateral membranes but also discernible in the cytoplasm. The staining of the NPE (but not the PE) showed clear-cut regional differences, and the presence of CA coincided with morphological indicators of secretory activity. Heavy staining was found in the capillaries under the ciliary epithelium. In the pars plana many capillaries showed staining of only that part of the circumference of the vessel wall which faced the epithelium. Unstained segments were also found in many choroidal capillaries under the pigmented epithelium of the retina. In the retina itself CA stain was found in the pigmented epithelium, in the Müller cells and in capillaries supplying the inner retina (only monkey retina was studied).(ABSTRACT TRUNCATED AT 250 WORDS)

Ornithine ketoacid aminotransferase in the bovine eye

Ornithine ketoacid aminotransferase in bovine ocular tissues was studied biochemically. The retinal pigment epithelium, ciliary body, iris, and neuroretina showed high specific activity. The cornea and choroid revealed a lower activity. Aqueous humor, lens, vitreous body, and sclera showed no activity. The pH optima of the enzyme in the retinal pigment epithelium and ciliary body were near 8.0.

Bicarbonate ATP-ase in ciliary body and a theory of Diamox effect on aqueous humor formation

Bicarbonate was found to stimulate ATP breakdown by rabbit or cat ciliary body-iris homogenates. Maximum HCO3- stimulation of ATPase with Tris-Hepes buffer occured at pH 8.0. Acid pH and chloride ions in the media reduced the activity of the HCO3--stimulated ATPase. The Km for ATP was 0.55 mmolar and for HCO3-, 20 mmlar. HCO3- ATPase was not inhibited by acetazolamide added to in vitro. It is postulated that ATPase represents the linkage step of energy donor mechanism and active CT secretion in acid aqueous humors (human, cat.) or HCO3- secretion in alkaline aqueous humor (rabbit, guinea pig). Inhibition of Cl- or HCO3- secretion by acetazolamide results from decreased intracellular HCO3- levels which, in turn, reduces the stimulation of the HCO3- ATPase.

Demonstration of tyrosinase in the adult bovine uveal tract and retinal pigment epithelium

Modern techniques offer an opportunity for a more complete evaluation of melanin production in the uvea and retinal pigment epithelium (RPE). By measuring the release of tritium from tritiated tyrosine in homogenized samples of adult bovine RPE as well as iris and choroid, tyrosinase activity could be demonstrated in both the uveal tract and the RPE. Phenylthiourea, a specific tyrosinase inhibitor, markedly decreased tyrosinase activity, whereas 3-iodo-tyrosine, a tyrosine hydroxylase inhibitor, had no effect. These techniques indicate tyrosinase activity in the uveal tract and the RPE of adult cattle. This is the first biochemical demonstration of tyrosinase in adult RPE.

[Effect of hydrocortisone on the concentration of serotonin and monoamine oxidase activity in the vascular tract of the eye]

Effect of hydrocortisone on content of serotonin was studied in eye vascular tract or blood and the monoamine oxidase (MAO) activity was estimated in eye vascular tract of young and adult rabbits at various periods after administration of hydrocortisone under conjunctiva. After administration of hydrocortisone content of serotonin was increased in eye vascular tract and decreased in blood. Maximal serotonin reaction was observed in vascular tract of adult rabbits within 24 hrs after the hydrocortisone treatment and in one-month-old rabbits--within 4-6 hrs. In blood of adult animals the most distinct decrease in serotonin content was found within 4-6 hrs after the single administration of the preparation; in one-month-old rabbits the effect was observed after the repeated treatment within 7 days. Effect of hydrocortisone on the MAO activity in eye vascular tract varied depending on the age. In one-month-old rabbits the MAO activity was increased distinctly within 24 hrs after single administration of the preparation and in adult animals the enzyme activity was decreased within 4-6 hrs and did not alter at the other periods after the hydrocortisone administration.

Inhibition of the prostaglandin synthetase systems in ocular tissues by indomethacin

1 We have compared the sensitivity of the prostaglandin synthetase systems derived from microsomal fractions of rabbit ocular tissues (anterior uvea, conjunctiva and retina) with other rabbit tissues such as the kidney medulla and spleen, to inhibition by indomethacin.2 Generation of prostaglandin-like activity by the microsomal fractions from added arachidonic acid varied with the tissue used. Highest activity was found in the kidney medulla, then in descending order, the conjunctiva, anterior uvea, spleen, retina and cornea.3 Indomethacin was most potent in the spleen (ID(50) 0.045 mug/ml) then in decreasing order in the kidney medulla, conjunctiva, anterior uvea and weakest in the retina, where the ID(50) for indomethacin was 50 mug/ml.4 The differential sensitivity to inhibition of the prostaglandin synthetase systems from different tissues is an important consideration in the development of new ocular anti-inflammatory agents.