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Results for “Aqueous Humor”

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PubMed1992

The measurement of fibronectin concentrations in human aqueous humor.

The concentrations of fibronectin in aqueous humor, measured by ELISA which was developed to detect fibronectin, ranged from 5 ng/ml to 100 ng/ml. Aqueous humor was aspirated from human eyes with cataracts and glaucomas using a 26 gauge needle through the peripheral cornea before making the limbal incision into the anterior chamber during surgery. The results of the study show that the average concentration and standard deviation of fibronectin was 0.136 +/- 0.192 microgram/ml in cataract eyes, and 0.962 +/- 0.918 microgram/ml in glaucoma eyes respectively. There was a statistically significant difference between both groups (p = 0.000). However, no significant differences according to age and sex were noted. There was no influence due to preoperative intravenous mannitol injection on fibronectin concentration. The source of aqueous fibronectin is still not clearly known and the mechanism of the higher concentration of fibronectin in glaucoma has not been clearly disclosed, however it is thought that normally present fibronectin is accumulated in the anterior chamber because it can not pass the aqueous outflow pathway, or that fibronectin production may be increased in glaucoma.

Adolescent↗

PubMed1982

[The studies on distributions of cefsulodin and cefotiam to human aqueous humor and cornea].

Distributions of cefsulodin (CFS) and cefotiam (CTM), new parenteral cephalosporins, to human aqueous humor and cornea were studied in comparison with those of sulbenicillin (SBPC) and cefazolin (CEZ), and pharmacokinetic analysis was made by theory of compartment model, to obtain the following results. 1. Maximum aqueous humor levels of CFS and CTM were noticed at 2.5 hours after the start of 1 g CFS or CTM administration by 30 minute intravenous drip infusion, with the levels of 3.6 micrograms/ml and 4.2 micrograms/ml respectively. On the other hand, in case of 5 g SBPC or 2 g CEZ administration maximum aqueous humor levels were 12.5 micrograms/ml and 5.2 micrograms/ml respectively. 2. The ratios of maximum aqueous humor level to plasma level of the same time in CFS, CTM, SBPC and CEZ were 15.0, 16.8, 6.4% and 5.5%. Distribution of CFS or CTM was 2 to 3 times better than that of SBPC or CEZ. 3. From the result of pharmacokinetic analysis, ratios of aqueous humor to plasma levels in area under curves (AUC) of CFS, CTM, SBPC and CEZ were 25.6, 29.9, 16.4% and 7.9% respectively. Maximum aqueous humor levels of CFS, CTM, SBPC and CEZ were 2.9, 3.6, 11.4 micrograms/ml and 4.3 micrograms/ml and biological half life of gamma-phase were 2.57, 2.31, 2.77 hours and 2.24 hours respectively. 4. Cornea levels of CFS or CTM at one hour after the start of 1 g CFS or CTM administration by 30 minutes intravenous drip infusion were 2.9 micrograms/g and 5.2 micrograms/g, and their ratios to plasma level were 7.5% or 14.3% respectively. In case of 5 g SBPC or 2 g CEZ administration, the cornea levels were 26.7 micrograms/g and 5.0 micrograms/g, and the ratios were 9.4% and 3.4% respectively. 5. From the above, the distribution of CFS or CTM to human aqueous humor and cornea is better than that of SBPC or CEZ, and it is considered that clinical usefulness of both CFS and CTM by parenteral administration is expected in intraocular infections.

Aged↗

PubMed2003

Noninvasive assessment of aqueous humor turnover in the mouse eye.

PURPOSE: To develop a noninvasive test for monitoring changes in aqueous humor turnover in the mouse eye. METHODS: After topical instillation of fluorescein, the rate of decay of fluorescence from aqueous humor and cornea was monitored in Black Swiss, C57 Bl6, and DBA 2J mice with a microscope equipped with epifluorescence and a charge-coupled device (CCD) camera. RESULTS: The rate of decay of fluorescence was identical in right and left eyes over an approximately 70-minute measurement period. The rate of decay was similar in normal mice aged 2 and 18 months. Pilocarpine and latanoprost, known to enhance aqueous humor outflow in humans, accelerated the decay of fluorescence. Levobunolol, known to inhibit aqueous humor inflow in humans, slowed decay. Dimethylamiloride, an inhibitor of the Na(+),H(+) exchanger that is known to act on cultured cells of both the ciliary epithelium and trabecular meshwork and to lower mouse intraocular pressure (IOP), enhanced decay. DBA 2J mice, in which secondary glaucoma develops, displayed a slower decay of fluorescence at 18 months of age than age-matched unaffected animals. CONCLUSIONS: Monitoring decay of fluorescence provides a noninvasive index of aqueous humor dynamics in the mouse eye that facilitates study of ocular hypotensive drugs and mouse models of glaucoma. Coupled with knowledge of IOP, it permits semiquantitative conclusions about the relative roles of aqueous humor inflow and outflow in conditions with altered IOP. Based on this approach, dimethylamiloride appears to lower mouse IOP primarily by enhancing outflow of aqueous humor.

Amiloride↗

PubMed2006

Melatonin concentrations in aqueous humor of glaucoma patients.

PURPOSE: To determine whether glaucoma patients exhibit an abnormal melatonin concentration in aqueous humor. DESIGN: Case-controlled study, laboratory investigation. METHODS: Aqueous humor and plasma samples of 28 patients with primary open-angle glaucoma and 31 nonglaucoma control patients were collected during surgery, and additional plasma samples were taken the night preceding surgery. Melatonin concentrations were determined using direct radioimmunoassay. RESULTS: This study shows detectable concentrations of melatonin in the aqueous humor of healthy humans (45% of subjects) and of glaucoma patients (36% of subjects) sampled in the morning, with similar levels of aqueous humor melatonin concentrations in both groups (6.4 +/- 9.3 standard deviation (SD) pg/ml and 3.6 +/- 1.9 pg/ml, respectively). We find no significant association between the severity of glaucoma and melatonin levels in aqueous humor or in plasma. CONCLUSIONS: Moderate and severe glaucoma does not appear to be associated with abnormal melatonin concentrations in aqueous humor, at least during the morning sampling period assayed in this study.

Aged↗

PubMed1989

Further studies on the flow of aqueous humor through microporous filters.

It has recently been shown that aqueous humor is able to obstruct flow through Nuclepore polycarbonate filters having flow dimensions similar to those found in the juxtacanalicular tissue (JCT). We undertook studies designed to identify the component(s) of aqueous humor responsible for this obstruction and to determine the mechanism of blockage. We conclude that aqueous humor contains two components (one of which is specific to aqueous) which, when simultaneously present, hydrophobically bind to microporous filters and lead to filter blockage. Some implications for aqueous humor flow through the JCT are briefly discussed.

Animals↗

PubMed1992

The source of protein in the aqueous humor of the normal monkey eye.

In vivo aqueous fluorophotometry, morphology, and computational modeling were combined to examine the source of protein and the pathway by which protein enters the aqueous humor of monkeys. A computational model was developed to determine the likelihood of a diffusional route for delivering plasma proteins from ciliary body capillaries via the iris to anterior chamber aqueous humor, bypassing the posterior chamber. Model predictions were compared to aqueous fluorophotometric data obtained from monkeys following a single intravenous injection of fluoresceinated horseradish peroxidase (F-HRP, 250 mg/kg body mass). Model predictions of the magnitude and time course of anterior chamber F-HRP concentration agree with the fluorophotometric measurements. For example, of anterior chamber F-HRP concentration as a percentage of initial plasma F-HRP concentration at 90 min and 180 min post-injection was predicted to be 0.02% and 0.05%, respectively, and was measured to be 0.01-0.03% and 0.03-0.06%, respectively. In addition, model predictions in the case of a constant plasma protein level also are consistent with experimental data. The steady-state anterior chamber total protein concentration as a percentage of plasma protein concentration was predicted to be 0.2% and was assayed to be 0.05-0.2%. As in our previous study of the normal rabbit eye, morphologic and tracer localization evidence combined with the good agreement between model predictions and experimental data lead to the conclusion that a significant amount of the plasma protein normally present in monkey aqueous humor originates in ciliary body capillaries and diffuses anteriorly through the iris and into the anterior chamber.

Animals↗

PubMed2003

Population pharmacokinetics of marbofloxacin in aqueous humor after intravenous administration in dogs.

OBJECTIVE: To evaluate, by use of population pharmacokinetics, the disposition of marbofloxacin in the aqueous humor after IV administration in dogs and identify its potential usefulness in the prophylaxis and treatment of intraocular infection. ANIMALS: 63 dogs. METHODS: Dogs received a single dose of marbofloxacin (2 mg x kg(-1), IV) at various time intervals before cataract surgery. Aqueous humor and blood samples were collected at the beginning of surgery. Marbofloxacin concentrations were measured by high-pressure liquid chromatography. Data were analyzed with a nonlinear mixed-effect model and, by use of population pharmacokinetic parameters, the time course of aqueous humor concentration was simulated for single doses of 3, 4, and 5.5 mg x kg(-1) IV. Pharmacodynamic surrogate markers and measured aqueous humor concentrations were used to predict in vivo antimicrobial activity. RESULTS: A maximum marbofloxacin concentration of 0.41 +/- 0.17 microg x mL(-1) was reached in the aqueous humor 3.5 hours after IV administration. In the post-distributive phase, marbofloxacin disappeared from aqueous humor with a half-life of 780 minutes. The percentage penetration into the aqueous humor was 38%. Predictors of antimicrobial effects of marbofloxacin (2 mg x kg(-1), IV) indicated that growth of the enterobacteriaceae and certain staphylococcal species would be inhibited in the aqueous humor. Marbofloxacin administered IV at a dose of 5.5 mg x kg(-1) would be predicted to inhibit growth of Pseudomonas aeruginosa and all strains of staphylococci but would not eradicate streptococcal infections. CONCLUSIONS AND CLINICAL RELEVANCE: Marbofloxacin administered IV can penetrate the aqueous humor of canine eyes and may be suitable for prophylaxis or treatment of certain anterior chamber infections.

Animals↗

PubMed1996

Dexamethasone-cyclodextrin-polymer co-complexes in aqueous eye drops. Aqueous humor pharmacokinetics in humans.

PURPOSE: To test an aqueous eye drop solution containing a high concentration of dexamethasone in a cyclodextrin-based drug delivery system. This system increases both drug solubility in aqueous eye drops and drug permeability into the eye, through drug cyclodextrin-polymer co-complexes. METHODS: 2-hydroxypropyl-beta-cyclodextrin is a water-soluble oligosaccharide that can be used to dissolve lipophilic drugs, such as dexamethasone, in aqueous solutions. Co-complexation with a polymer further increases the solubility and increases drug permeability through biologic membranes. Eye drops containing dexamethasone (0.32% and 0.67%), 2-hydroxypropyl-beta-cyclodextrin, and polymer were given to patients before cataract surgery, and the resultant dexamethasone concentration was measured from aqueous humor samples. RESULTS: The dexamethasone-cyclodextrin drops give a significantly higher concentration of dexamethasone in aqueous humor than dexamethasone alcohol 0.1% (Maxidex). Heating of the dexamethasone-cyclodextrin-polymer co-complexes appears to enhance the permeability of the drug into the eye. CONCLUSIONS: The cyclodextrin-based drug delivery system enhances both the solubility of dexamethasone in aqueous eye drops and the permeability of the drug into the human eye. Dexamethasone concentration levels in the human aqueous humor exceed those reported with currently available steroid eye drops.

2-Hydroxypropyl-beta-cyclodextrin↗

PubMed1992

Quantitative and qualitative analyses of transferrin in aqueous humor from patients with primary and secondary glaucomas.

By using a highly sensitive and specific radioimmunoassay and the slot-blot technique, transferrin was quantified in fresh samples of aqueous humor from patients with primary open-angle glaucoma (POAG, n = 36) or secondary glaucoma (SG, n = 18). The levels were compared with those in aqueous humor obtained from age-matched patients without glaucoma (n = 33) and in primary and secondary aqueous humor from normal dogs (n = 10) in which breakdown of the blood-aqueous barrier was induced experimentally. The concentration of transferrin in the aqueous humor of human control subjects ranged from 0.3-3.4 mg/dl (mean +/- standard deviation, 1.36 +/- 0.66 mg/dl); in POAG samples, from 0.34 to greater than 10 mg/dl (2.07 +/- 1.90 mg/dl); and in SG samples, from 0.29 to greater than 10 mg/dl (2.79 +/- 2.24 mg/dl). The level of transferrin in secondary aqueous humor samples obtained from dogs was as much as ninefold greater than that in primary aqueous humor. The protein concentration in the human aqueous humor samples was 11.87 +/- 4.47 mg/dl for control subjects, 62.11 +/- 56.74 mg/dl for patients with POAG, and 124.53 +/- 152.67 mg/dl for those with SG. In dogs, the protein levels were 7.97 +/- 3.12 mg/dl for primary aqueous humor and 191.9 +/- 149.8 mg/dl for secondary aqueous humor. A significant correlation (r = 0.744, P less than 0.01) was found between total protein and transferrin contents in the samples of aqueous humor from patients with glaucoma but not in the samples from age-matched control subjects.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMedDate not supplied

Comparison of free amino acids in aqueous humor of farmed and wild salmon and of six species additionally.

OBJECTIVE: A comparative study was performed in order to identify aqueous humor amino acids possibly involved in cataract formation in farmed Atlantic salmon. METHODS: Aqueous humor amino acids from farmed salmons with and without cataract were compared with levels in wild salmon and other animals of different evolutionary levels such as frog, crocodile, turkey, goose, minke whale, and cattle. Serum samples from wild and farmed salmon and minke whale were also analyzed. RESULTS: The total amino acid concentration was lower in aqueous humor obtained from salmon, frog and crocodile compared to birds and mammals. Wild salmon had a higher content of amino acids than farmed salmon. Asparagine was absent in salmon aqueous humor and serum. Aqueous humor proline was readily detectable in wild salmon, birds, whale, and cattle, but not detectable in farmed salmon, frog and crocodile. The aqueous humor concentration of taurine was about seven- and fifty-fold lower compared to serum in wild and farmed salmon, respectively. The corresponding ratio in minke whale was 1:2. CONCLUSIONS: The results indicate a blood- aqueous barrier for taurine in farmed salmon. The lower total amino acid concentration and low aqueous humor proline concentration in farmed salmon should be further investigated.

Amino Acids↗

PubMed1990

Tau fraction of transferrin is present in human aqueous humor and is not unique to cerebrospinal fluid.

In view of the many similarities between the aqueous humor and the cerebrospinal fluid (CSF), we investigated whether the tau fraction of transferrin, which is believed to be specific for CSF, is also present in aqueous humor. Samples of aqueous humor and CSF from clinically normal individuals were analyzed by SDS-PAGE and isoelectric focusing (IEF), and probed with anti-transferrin antiserum and the lectin Limax flavus agglutinin. Specific bands which corresponded to transferrin and its tau fraction were detected in both fluids. After isolation of these bands by affinity chromatography with anti-transferrin antiserum, we detected a single, diffuse fraction at an apparent molecular weight of 80 kDa in both aqueous humor and CSF. Peptide mapping revealed no detectable difference in this fraction between the two fluids. The detection of the tau fraction in human aqueous humor indicates that this molecule cannot be considered a specific cerebrogenic marker as had been thought previously. In view of the known growth-promoting properties of transferrin, its isolation from both ocular and cranial fluids attains special significance.

Aged↗

PubMedDate not supplied

[The resistance to drainage of the aqueous humor].

The presence of the evacuation paths of aqueous humor at the level of the camerular angle makes it play an important role on open angle glaucoma pathology. The fundamental element in the evacuation of aqueous humor is the endothelial cell, who has a main contribution to the routing of aqueous humor using the phenomenon called micropinocytosis. With the age the number of endothelial cells diminishes, their function reduces and an atypical collagen appears, together with the thickness of the basal membrane, the agglutination of the trabecular blades and Schlemm channel collapse. The fact is that the raise of the evacuation resistance in open angle glaucoma must not be interpreted mechanically; a research from a biochemical and molecular point of view must be completed.

Aqueous Humor↗

PubMed2002

Vascular endothelial growth factor is increased in aqueous humor of glaucomatous eyes.

PURPOSE: To assess the concentrations of vascular endothelial growth factor (VEGF) in aqueous humor in eyes with and without glaucoma. METHODS: Concentrations of VEGF were measured using a sandwich ELISA kit in aqueous humor aspirates taken during anterior segment surgery from 87 patients, of whom 54 had glaucoma (27 primary open-angle glaucoma, 8 angle-closure glaucoma, 16 exfoliative glaucoma) and 33 had cataract only. RESULTS: Vascular endothelial growth factor was detected in all samples. The concentration in eyes with cataract only without glaucoma was 102.4 +/- 29.7 pg/mL (mean +/- SD), which was significantly lower than that from eyes with glaucoma (146.7 +/- 51.8 pg/mL). There were no significant differences between primary open-angle glaucoma (140.4 +/- 51.0 pg/mL), angle-closure glaucoma (142.8 +/- 40.2 pg/mL), and exfoliative glaucoma (158.6 +/- 58.9 pg/mL). An unusually high VEGF concentration was detected in one eye with neovascular glaucoma (759 pg/mL) and two eyes with uveitic glaucoma (322 pg/mL). No effect of age, gender, or previous history of medical, laser, or surgical treatment of the aqueous humor VEGF concentration could be detected ( > 0.05). Aqueous humor and plasma VEGF concentrations were measured and compared in 46 patients. The aqueous humor VEGF concentration (144.2 +/- 107.9 pg/mL) was significantly higher ( < 0.01) than the plasma concentration (79.2 +/- 46.1 pg/mL). No significant correlation was found between aqueous humor and plasma VEGF concentrations. CONCLUSION: Aqueous VEGF concentration is increased in eyes with glaucoma.

Aged↗

PubMed1997

Plasma and aqueous humor endothelin levels in primary open-angle glaucoma.

PURPOSE: Endothelins (ET) have some effects on the regulation of aqueous humor dynamics. To investigate their possible role in glaucoma, we measured plasma and aqueous humor ET levels in patients with and without primary open-angle glaucoma. METHODS: Plasma and aqueous humor samples were obtained from 31 patients with primary open-angle glaucoma and 24 patients without glaucoma. Measurements were made by radioimmunoassay (RIA) for ETs with the following cross-reactivities: ET-1, ET-2, and big ET-1, 100%; and ET-3, 70%. RESULTS: The ages (mean +/- SD) of the patients with primary open-angle glaucoma (72.3 +/- 10 years) and normal subjects (72.8 +/- 8 years) were similar (p = 0.92). There was no significant difference between plasma ET levels of the two groups (p = 0.07). However, aqueous humor ET levels (mean +/- SD) were higher in the primary open-angle glaucoma group (44.26 +/- 2.6 pg ml-1) than in normal subjects (42.17 +/- 1.6 pg ml-1) (p = 0.001). The ratios of corresponding aqueous humor to plasma levels of ETs were approximately 10% higher in the primary open-angle glaucoma group (3.76) than in normal subjects (3.41) (p = 0.0002). CONCLUSIONS: The small increase in aqueous humor endothelin levels in patients with primary open-angle glaucoma versus controls of similar age may be relevant to the understanding of the various roles of ETs in aqueous humor dynamics in these patients.

Aged↗

PubMedDate not supplied

Nitric oxide levels of aqueous humor after photorefractive keratectomy.

PURPOSE: To measure the nitric oxide (NO) levels of aqueous humor in rabbits after photorefractive keratectomy (PRK) and to evaluate the alterations of NO levels according to the PRK surgery steps, ablation depth, and time. METHODS: Fifty eyes of 25 New Zealand white rabbits were included in the study. One eye was later randomly excluded from the study in order to equalize the number of eyes in groups. Eyes were divided into seven groups, each comprising seven eyes: unwounded control (Group 1), epithelial scrape (Group 2; aqueous humor samples taken at the 4th hour), superficial PRK (Group 3; samples taken at the 4th hour), deep PRK (Group 4; samples taken at the 4th hour), epithelial scrape (Group 5; samples taken at the 24th hour), superficial PRK (Group 6; samples taken at the 24th hour), and deep PRK (Group 7; samples taken at the 24th hour). The corneal epithelium was mechanically removed in surgical groups. The authors performed superficial corneal ablation (59 microm) in Groups 3 and 6 and deep corneal ablation (99 microm) in Groups 4 and 7. Aqueous humor samples were taken at the 4th hour (Groups 2-4) or 24th hour (Groups 5-7) after corneal surgeries. NO measurements were performed indirectly by using the Griess reaction with a spectrophotometer. RESULTS: Aqueous humor NO levels 4 hours after corneal surgery were statistically significantly lower than the control group (p<0.05). However, there was no difference among the surgical groups at the 4th hour (p>0.05). At the 24th hour, the deep PRK group had significantly lower NO levels than both the control group and Groups 5 and 6 (p<0.05). NO levels were normalized at the 24th hour in epithelial scrape and superficial PRK groups (p>0.05) but remained stable at lower levels in deep PRK groups (p<0.05). CONCLUSIONS: Corneal surgery caused low NO levels in aqueous humor 4 hours after surgery. However, 24 hours after surgery, NO levels normalized following epithelial scrape and superficial PRK and were stable at lower levels in the deep PRK group. Complications of deep PRK application are possibly induced by low NO existence in the aqueous humor.

Analysis of Variance↗

PubMed2005

Primary trabecular meshwork cells incubated in human aqueous humor differ from cells incubated in serum supplements.

PURPOSE: To determine whether aqueous humor, the in vivo source of nutrients for trabecular meshwork cells, alters cellular and molecular characteristics in primary trabecular monolayer cell cultures when compared with standard culture conditions. METHODS: Human primary trabecular meshwork cell cultures were grown in DMEM supplemented with 50% human aqueous humor (DMEM-AH), heat-denatured DMEM-AH, 10% fetal bovine serum (DMEM-FBS, the standard culture supplement), or heat-denatured DMEM-FBS. Confluent trabecular cells were assayed for cell propagation and morphology for 21 days. Protein expression profiles of trabecular cell lysates were analyzed by two-dimensional polyacrylamide gel electrophoresis. Western blot analysis was used to determine the protein expression of myocilin and TIMP-1 in conditioned media collected from trabecular cells at 5, 10, 15, and 21 days. Myocilin expression was also analyzed by Western immunoblots after addition of dexamethasone (10(-7) M) or ascorbic acid (29 mg/dL). RESULTS: Trabecular cells supplemented with DMEM-AH for 21 days showed decreased cell proliferation when compared with DMEM-FBS (11% vs. 141%). Cellular morphology was also altered: Trabecular cells incubated in DMEM-AH showed larger-, broader-, and flatter-appearing cells than did the more spindle-shaped cells grown in DMEM-FBS. Protein profiles of trabecular cell lysates isolated from cells incubated in DMEM-AH differed from those incubated in DMEM-FBS. In DMEM-AH-conditioned medium, myocilin expression was increased and TIMP-1 expression was decreased at day 21. Induction of myocilin by dexamethasone was observed in conditioned medium isolated from cells treated with DMEM-FBS (442%), but only a 10% increase in myocilin was observed beyond the normal induction in DMEM-AH. Daily administration of ascorbic acid to DMEM-AH failed to increase myocilin expression beyond that obtained with DMEM-AH. CONCLUSIONS: Addition of human aqueous humor rather than FBS to trabecular monolayer cell cultures triggers significant changes in cellular and molecular characteristics. The protein component of aqueous humor is responsible for these changes. Aqueous humor supplementation may maintain cultured trabecular cells in a more physiologic state.

Adult↗

PubMed1999

Aqueous humor dynamics in alpha-chymotrypsin-induced ocular hypertensive rabbits.

Aqueous humor dynamics were studied in alpha-chymotrypsin-induced ocular hypertensive rabbits either by tonographic or two-level constant pressure perfusion techniques. A significant correlation was obtained between the values of outflow facility in alpha-chymotrypsin-induced ocular hypertensive rabbits as determined by tonography and constant pressure perfusion. The mean value of tonographic outflow facility in ocular hypertensive rabbits was not statistically different from that found in ocular normotensive rabbits. On the contrary, the estimated rate of aqueous inflow in ocular hypertensive rabbits was about 1.5-fold higher than that of ocular normotensive ones. While topical timolol lowered intraocular pressure and aqueous humor inflow in ocular hypertensive rabbits, pilocarpine did not produce any significant effect. Aqueous humor protein was significantly increased in ocular hypertensive eyes. The results of this study show that accurate measurements of outflow facility can be obtained in alpha-chymotrypsin-induced ocular hypertensive rabbits by tonographic technique. Our data suggest that the long-term ocular hypertension induced by alpha-chymotrypsin in albino rabbits may be secondary to an increase in the rate of aqueous humor inflow, likely produced by a breakdown of the blood-aqueous barrier. This finding strongly conflicts with the hypothesis of trabecular blockage as the cause of alpha-chymotrypsin-induced ocular hypertension in this species.

Animals↗

PubMed1975

The rates of ion movement from plasma to aqueous humor in the dogfish, Squalus acanthias.

Aqueous humor dynamics were studied in the dogfish, Squalus acanthias, using isotopically labeled inulin, Na+, Cl-, and HCO-3. Fluid production was 100 mul per hour, with a turnover rate constant of 0.4 hr.-1, about half that of mammals. The ciliary process contains carbonic anhydrase and Na-K-ATPase. Diffusion of Na+ and Cl- from plasma to aqueous was four to five times greater than flow, and from aqueous to vitreous, about 15 times greater. Sodium and chloride secretion is masked by the diffusion process; neither ouabain nor acetazolamide yield measurable effects on accumulation of these isotopes. HCO-3 accumulation in aqueous was very rapid and was reduced by inhibition of carbonic anhydrase. Analyses of the data suggest that newly formed aqueous has similar Na+ concentration to plasma, but is high in HCO-3 and low in Cl-. This anion pattern resembles mammalian aqueous humor, and cerebrospinal fluid and endolymph of other vertebrates. These and other data suggest that constant features of formation of these fluids in all phyla are sodium transport and formation of HCO-3 from CO2.

Acetazolamide↗