Morton B. Waitzman

Some characteristics of an adenyl cyclase preparation from rabbit ciliary process tissue

Abstract A particulate adenyl cyclase preparation from quick-frozen rabbit ciliary process tissue has been shown to be activated by 50 m m KCl, 10 m m NaF, catecholamines and prostaglandin E 1 . Catecholamine activation appears to be of the β-adrenergic type. Prostaglandin E 1 and β-adrenergic activation seem to be additive. Prostaglandin E 1 and α-adrenergic effects appear to be antagonistic.

Effects of some steroids on aqueous humor dynamics

We have performed tonographic and histological studies in rabbits, using several locally applied steroid preparations, with a view to analyzing the progression of an ocular hypertensive state. Two of the preparations tested (6α-methylprednisolone 21-acetate and dexamethasone 21-phosphate) induced a dual intraocular pressure response. The third preparation, aldosterone, induced a sustained hypotension. When dexamethasone 21-phosphate was applied topically, a quick drop in pressure, accompanied by an increase in outflow, was observed. This was followed by a small, but significant, rise in intraocular pressure after 2 weeks. Aldosterone was applied subconjunctivally and topically to separate groups of rabbits daily for 14 days. Sustained decreases in intraocular pressure occurred. The administration of 6α-methylprednisolone 21-acetate twice weekly for 2 weeks caused a prolonged hypotensive effect. Single doses of the same drug produced a lowering of the intraocular pressure 3 hr after administration, reaching a maximum effect in 2–4 days. This drop in intraocular pressure was accompanied by a large increase in facility of outflow. Almost identical ocular responses, with no signs of toxicity, were evoked with lower doses of 6α-methylprednisolone 21-acetate. Again, the initial hypotensive response was followed by a hypertensive phase. The response to this steroid was the same on eight occasions in five separate groups of animals. It occurred in old, middle-aged and young animals, it was not invoked by the vehicle or by any premedication used, and it was not produced by changes in ocular rigidity. Tonography suggested that the drop in intraocular pressure was caused by some structural change in the filtration angle. Attempts were made to evaluate these structural changes on the basis of histological findings.

Chromatographic analysis of biologically active lipids from rabbit irides

Extraction of lipids from rabbit irides and subsequent gas-liquid and thin-layer chromatographic analysis of these extracts revealed the presence of a very low concentration of a biologically active substance(s). The active substance(s) represents one or more derivatives of prostanoic acid containing one or more hydroxyl groups in the molecule. Because these materials had little effect on ocular pressure, but did reduce pupil size in rabbits, it is likely that the active material is in the prostaglandin F family of compounds.

Proposed metabolic dysfunctions in diabetic microthromboses and microangiopathy.

This report describes, at least in part, the role of prostaglandin and cyclic nucleotide metabolism in the etiology of the vascular disease associated with diabetes mellitus. Alterations in this metabolism seem associated with induction of platelet aggregation leads to microthromboses leads to microangiopathy sequences that are subtle but inexorable over a long period of time. Prostaglandins are generally elevated in blood from patients having frank signs of diabetic retinopathy when compared with nondiabetic subjects. Prostaglandin concentration remained elevated in diabetic retinopathy patients receiving indomethacin. We formed, therefore, the working hypothesis--yet to be fully tested either in patients or animal models with and without indomethacin treatment--that the increased prostacyclin (synthesized by endothelial microsomes) and cyclic-AMP production, both of which favor prevention of platelet aggregation, accompany the increased concentration of one or more of the prostaglandin E and F compounds. Concurrently, there may be an accompanying reduction of thromboxane A2 (synthesized by platelet microsomes) and cyclic-GMP (both of which favor platelet aggregation) production in the diabetic patients. The elevated prostaglandin in the diabetic patients not receiving indomethacin could possibly be directed toward slowing but not preventing the progression of the complex disease process in diabetes.

Pupil size and ocular pressure after sympathectomy and prostaglandin-catecholamine treatment.

Interaction between prostaglandin E1 and norepinephrine relative to effects on ocular pressure and pupil size was studied in albino rabbits in which unilateral cervical sympathetic ganglionectomy was performed. The operated animals, at the time of prostaglandin-norepinephrine interaction studies, were pretreated with phenoxybenzamine prior to each study. That dose of norepinephrine which was ineffective in altering ocular effects of prostaglandin in unoperated animals was now effective in antagonizing the ocular effects of prostaglandin in ganglionectomized animals. Supersensitivity of norepinephrine relative to these drug interaction studies was thus demonstrated.

Effects of topically administered ouabain on aqueous humor dynamics.

Repeated topical administration of ouabain has been shown to induce a hypodynamic state in both normal and buphthalmic rabbit eyes. The fall in intraocular pressure is greater with increasing concentrations of ouabain. When 0·25% or 0·125% ouabain solutions are used on buphthalmic rabbits, a lowering of the intraocular pressure is observed within 2 hr. This effect persists for about 3 days. Responsiveness does not appear reduced when tests are repeated frequently in the same animal. The histological evidence in buphthalmic eyes suggests that the elevated intraocular pressure in these eyes is most likely related to a deficient drainage mechanism and that lowering of the intraocular pressure by a drug such as ouabain is due, primarily, to an inhibition of aqueous humor secretion.

Prostaglandins and diabetic retinopathy

Our preliminary information indicates that there is an elevation of at least one particular prostaglandin, i.e. prostaglandin F2α, in the serum of the diabetic patient who has diabetic retinopathy. We can only speculate on the relationship that this bears with the altered fatty acid metabolism in the diabetic; but, the prospects would appear quite good that positive correlations between altered lipid metabolism (involving prostaglandins) and diabetic disease will evolve.

INFLUENCES OF CHLORPROMAZINE ON AQUEOUS HUMOR DYNAMICS

The use of chlorpromazine (Thorazine) in glaucoma therapy has been described by Bierent (2). In an attempt to elucidate these anti-glaucoma effects of chlorpromazine, Paul and Leopold studied the intraocular pressure (1OP)-lowering effects of this drug in rabbits and cats (3). These latter investigators also correlated the IOP changes with changes in pupil size using doses of chlorpromazine which appeared to range between 10 and 40 mg/kg in rabbits, and 20-40 mg/kg in cats. The IOP-lowering effects, which seemed unrelated to pupil size, seem similar for both species for similar doses of this drug. These effects were from 5 to 20 mm Hg. depending on dose. In this study we were interested not only in IOP and aqueous flow effects of chlorpromazine, but also, in the usefulness of this drug in reducing to a minimum-excitement-related influences of animal manipulation on tonography.

Effects of subconjunctivally administered ouabain on aqueous humor dynamics

These studies have demonstrated the effectiveness of subconjunctivally administered ouabain in inducing a hypodynamic state in rabbit eyes associated with changes in aqueous humor composition. Although the intraocular pressure and the aqueous secretion were significantly reduced and the facility of outflow was significantly increased under the influence of ouabain, the marked shifts in aqueous composition which we observed would lead one to the conclusion that primarily the aqueous secretion was affected. The results indicate, too, that the onset of ouabain effects was quite rapid (within ½–1 hr) and that changes in ocular dynamics relative to chemical composition were most dramatic during the first day after a single injection, with residual effects lasting up to 5 days.

Changes in prostaglandin concentration in blood subjected to repetitive freezing and thawing.

Successive freezing and thawing of whole blood results in a consistently higher yield of various prostaglandin (PG) compounds. Evaluations were made with radioimmunological assay. The increase in PG concentrations seems to be more associated with cell fragmentation and not with the dissociation of albumin-PG complex. Our data suggest that there may be some dissociation of non-albumin-PG complexes. Artifactually high PG concentrations due to in vitro PG synthetase activity appears minimal at least with respect to indomethacin blocking of this enzyme. There are, in general, only slight differences in PG concentrations in samples with and without indomethacin.