the solution additive such as to an irrigation solution or a surgical solution is used at a concentration of 1 - 100 parts for each 500 parts of a commercially available balanced salt solution ( bss ) base such as that sold by iolab or alcon . typically , the additive concentrate contains one or more of the components in table a . table a______________________________________ preferredcomponent range component______________________________________glycosaminoglycan 0 . 001 - 550 mg / ml chondroitin sulfatean antioxidant 0 - 10 mm 2 - mercaptoethanolenergy source 0 - 20 mm dextrose 0 - 20 mm pyruvateamino acid 0 - 10 mm cystinebuffer 0 - 100 mm sodium bicarbonate______________________________________ the formulation is a representative concentration of the additive made up in a total volume of 1 - 50 ml balanced salt solution or water . the additive can then be added to 500 ml of balanced salt solution as in table b . this irrigation solution additive is therefore defined at proportionate concentrations at all other volumes table b______________________________________additive of 50 ml made up in______________________________________balance salt solution ( bss ) base medium : chondroitin sulfate 44 . 00 mg / ml2 - mercaptoethanol 5 . 50 mmdextrose 55 . 0 mmpyruvate 11 . 00 mmcystine 33 . 00 mmsodium bicarbonate 275 . 00 mmbalance salt solution ( bss ) base medium : sodium chloride . 64 % potassium chloride . 075 % calcium chloride . 048 % magnesium chloride . 030 % sodium acetate . 39 % sodium citrate . 17 % ______________________________________ or made up in distilled injection grade water . the final concentration of the additive after dilution with an appropriate amount of balance salt solution is described in table c . table c______________________________________final concentration approximate final ranges ofcomponent concentration final concentration______________________________________chondroitin sulfate 4 . 00 mg / ml ( 0 - 100 mg / ml ) 2 - mercaptoethanol 0 . 50 mm ( 0 - 2 mm ) dextrose 0 . 92 mg / ml ( 0 - 20 mm ) pyruvate 1 . 00 mm ( 0 - 20 mm ) cystine 1 . 00 mm ( 0 - 10 mm ) sodium bicarbonate 25 . 00 mm ( 0 - 100 mm ) ______________________________________ this additive is therefore defined at proportionate concentrations at all other volumes . an additive concentrate comprising one or more of the following components in balanced salt or like solution . ( lyophilized ) 1 . laminin , a large glycoprotein having a molecular weight of approximately 1 , 000 , 000 daltons . the laminin molecule has the shape of an asymmetric cross , comprised of 3 b chains of 200 , 000 daltons each , and one a chain of 400 , 000 daltons . the chains are held together by disulfide bonds . the single a chain contains a binding site for heparin sulfate . the b chains contain type iv collagen binding sites . the intersection of the three b chains is the locus for cell binding . laminin provides cells with physiological compatible extracellular matrix that will foster attachment cytoplasmic spreading and proliferation . 2 . fibronectin is an extracellular matrix - associated glycoprotein composed of two disulfide bonded subunits of 220 , 000 daltons each . fibronectin has the potential to interact with several cell surface associated macromulecules including collagen , glycosaminoglycans and cell surface receptors . fibronectin promotes cell adhesion and migration of human corneal endothelial cells , epithelial cells and fibroblasts . 1 . fibroblastic growth factor ( fgf ), a single chain polypeptide , isolated and purified from the pituitary , human ( hfgf ) fibronectin or bovine fibronectin ( bfgf ), acidic or basic forms . molecular weight range of 14k to 16k . this factor has been demonstrated mitogenic in vitro to a wide variety of cells comprising mesoderm and neuroectoderm tissue . this also includes synthetic formulated fgf basic peptides consisting of : ( 1 - 24 ) 2 . endothelial cell growth supplement ( ecgs ), prepared from the hypothalamus as a lyophilized extract . this growth supplement has demonstrated mitogenic in vitro to a wide variety of endothelial cells ; i . e ., human corneal endothelial cells , human umbilical vein endothelial cells , and mouse balb / c fibroblasts . 3 . urogastrone or epidermal growth factor ( egf ), a single chained polypeptide , is composed of 53 amino acids , containing 3 disulfide bonds and has been isolated from mouse submaxillary glands ( megf ) and human urine ( hegf ). this growth factor has been demonstrated to be mitogenic in vitro for a wide variety of cells of ectodermal and mesodermal origin . 4 . bovine pituitary extract ( bpe ) an aqueous extract of bovine or human pituitary glands . this growth supplement has demonstrated mitogenic in vitro to a wide variety of epithelial cells ; i . e ., human corneal epithelium , human epidermal keratinocytes 5 . insulin a polypeptide hormone that functions in the regulation of cellular carbohydrate metabolism and the synthesis of cellular protein , rna and neutral lipids . 1 . iv collagen : the main collagen in basal laminae . iv collagen in a range of about 5 mg / ml - 10 g / ml . effect of two hour irrigation with balanced salt solution with additive without cystine on the glutathione content of cat lenses to determine that the in vitro effects of 2 - mercaptoethanol could be duplicated in vivo , the following studies were done . in two hour anterior chamber perfusion studies , using a balanced salt solution with additive ( chondroitin sulfate 4 . 0 mg / ml ; 2 - mercaptoethanol 0 . 5 mm ; dextrose 0 . 92 mg / ml ; pyruvate 1 . 0 mm ; sodium bicarbonate 25 mm ) ( without cystine ) in cats , the glutathione content of the lens was compared to the non - irrigated control 24 hours after perfusion . ______________________________________ irrigation with additive control______________________________________total 1530 . 27 ± 26 . 03 ug / lens 1435 . 39 ± 46 . 39 ug / lensglutathione6 . 20 % difference______________________________________ a 6 . 2 % difference in total glutathione was seen between the irrigated lens and the control lens . this increase in glutathione content is due to de novo synthesis . effect of two hour irrigation with balanced salt solution with additive containing 3 mm cystine on the glutathione content of cat lenses to determine if the in vivo effect of the irrigation additive , containing 2 - mercaptoethanol , could be enhanced by the addition of 3 mm cystine , the following studies were done . in two hour anterior chamber perfusion studies , using a balanced salt solution with the additive containing 3 mm cystine , in cats , the glutathione content of the perfused lens was compared to the non - irrigated control 24 hours after perfusion . ______________________________________bss with additive with 3 mm cystine control______________________________________total 1495 . 73 ± 35 . 75 ug / lens 1378 . 25 ± 31 . 25 ug / lensglutathione7 . 85 % difference______________________________________ a 7 . 85 % increase in total glutathione was seen between the irrigated lens and the control lens . this increase in glutathione content is due to de novo synthesis . balanced salt solution with additive containing 3 mm cystine appears to have enhanced the effect of 2 - mercaptoethanol , in vivo by increasing the lens concentration of glutathione . the effect of 2 - mercaptoethanol on human and rabbit lens in vitro in the investigational work with human corneal endothelial cells , it is recognized the limited capacity to synthesize cystine via the methionine pathway . in addition , corneal endothelial cells are deficient in capacity to uptake cystine , and that intracellular cystine and glutathione contents decrease considerably in normal culture medium containing cystine . then examined was the glutathione content of human and rabbit lenses . reduction of glutathione content in human lens has been associated with the formation of certain types of cataracts . glutathione is made up of three amino acids , cystine , glutamic acid , and glycine . cystine has been implicated as the limiting amino acid for the synthesis of protein as well as glutathione . an increase in the intracellular cystine pool by the addition of 2 - mercaptoethanol may cause the increase in cellular glutathione content , because the cellular pool of cystine is very low as compared with that of glutamic acid and glycine . in three days , in vitro rabbit lens incubation studies utilizing 2 - mercaptoethanol , the glutathione content of the lens was compared to the control lens incubated without mercaptoethanol . ______________________________________ medium with 2 - mercaptoethanol control______________________________________total 657 . 61 ± 24 . 70 ug / lens 615 . 5 ± 24 . 70 ug / lensglutathionepercent 3 . 94 8 . 54oxidized6 . 4 % difference in total glutathione______________________________________ only a small difference in total glutathione was found in these studies . the rabbit lens is capable of producing enough cystine to maintain intracellular glutathione levels during lens incubation in vitro . the 2 - mercaptoethanol was able to maintain the glutathione in a reduced form greater than the control . in three day , in vitro human lens incubation studies utilizing 2 - mercaptoethanol , the glutathione content of the lens was compared to the control lens incubated without 2 - mercaptoethanol . ______________________________________ medium with 2 - mercaptoethanol control______________________________________total 230 . 91 ± 15 . 49 ug / lens 176 . 16 ± 2 . 26 ug / lensglutathionepercent 13 . 02 17 . 87oxidized23 . 70 % difference in total glutathione______________________________________ with the media containing 2 - mercaptoethanol , there was a 23 . 7 % increase in the total glutathione content mainly in the reduced form . the base of this additive is a completely defined balance salt solution supplemented with dextrose and with the addition of one to five corneal and retinal enhancing agents . these are chondroitin sulfate , 2 - mercaptoethanol , pyruvate , cystine , and sodium bicarbonate . the exposure time to the additive solution in the normal ophthalmic surgical procedure , such as an intraocular lens implant , is normally 3 - 8 minutes , a very limited time period . but upon special occasions , the anterior chamber is filled with the solution and allowed to remain there until the aqueous humor is remade , which may take up to 24 hours . during this time the anterior chamber cells are deprived of necessary nutrients , normally supplied by the aqueous humor . although the anterior segment cells , most significantly the corneal endothelium , are supplied with nutrients from their basal side , most of the metabolic uptake is from the anterior surface . the corneal endothelium maintains the clarity of the cornea by actively pumping salts and water out of the connective tissue stroma into the anterior chamber of the eye . the na + / k + atpase pump of these endothelial cells requires atp and reduced pump sites to keep this pump working . when the pumping action of these corneal endothelial cells is reduced , the cornea imbibes fluids and becomes thickened and loses optical clarity . therefore , an irrigation solution with an additive with a reducing agent is of considerable advantage . one of the major disadvantages of bss plus , with the reducing agent glutathione and the bicarbonate buffering system , is the lack of stability of the solution once prepared . the glutathione component of the solution is added separately , and the solution is stable for only a 24 hour period . the buffering ability of the bicarbonate in bss plus is greatly reduced once the solution is exposed to the atmosphere . the present additive provides the reducing agent 2 - mercaptoethanol , that can be utilized in both the reduced and oxidized forms eliminating the instability of a glutathione containing irrigation solution . this effective reducing agent can be utilized by human corneal endothelial cells . five additional components have been added to the solution to increase its effectiveness in protecting and repairing the anterior segment of the cornea during and after surgical trauma . ( 1 ) chondroitin sulfate , a highly negative charged glycosaminoglycan is added to replace any glycosaminoglycans that may be removed from the surface of the corneal endothelial cells from the disruption of aqueous flow or surgical trauma . glycosamimoglycans are necessary for membrane stability and the maintenance of the three - dimensional structure of receptor proteins . these receptor proteins are required for the metabolic processes of the cell . chondroitin sulfate acts as a protective coating for the anterior segment cells . an additional substrate , ( 2 ) pyruvate , is provided for additional biosynthetic synthesis that may be required by these anterior segment cells after surgical trauma . there are 20 standard amino acids in proteins , all having different carbon skeletons . correspondingly , there are 20 different catabolic pathways for their degradation . carbon skeletons of 10 of the amino acids are ultimately broken down to yield acetyl - coa which enters the citric acid cycle directly . five of the ten are degraded to acetyl - coa via pyruvate . the five amino acids entering via pyruvate are alanine , cystine , glycine , serine , and threonine . ( 3 ) 2 - mercaptoethanol , an anti - oxidant , used in the proposed irrigation additive has been shown to be effective at concentrations of 10 to 1000 μm , and its action resembles those of macrophages or feeder layer cells . it is proposed that human corneal endothelial cells have a low capacity to synthesize cystine via the methionine pathway . methionine furnishes the sulfur atom and serine furnishes the carbon chain in the biosynthesis of cystine . the end result of a complex series of reactions is the replacement of the -- oh group of serine with an -- sh group , derived from methionine , to form cystine . in addition , corneal endothelial cells are deficient in their capacity to take up cystine and that intracellular cystine and glutathione contents decrease considerably in normal culture medium containing cystine . in the presence of 2 - mercaptoethanol , corneal endothelial cells constantly utilize ( 4 ) cystine in the irrigation solution and the cellular cystine and glutathione levels are maintained during intraocular perfusion . this effect seems to be the most crucial function of 2 - mercaptoethanol in stimulating the growth of the cells and is not explained by mere reduction of cystine to cystine in the irrigation solution . it is the mixed disulfide of 2 - mercaptoethanol and cystine , which is formed by the reaction of 2 - mercaptoethanol with cystine in the irrigation solution , that plays an important role in the action of 2 - mercaptoethanol . the 2 - mercaptoethanol acts repeatedly as a carrier of cystine . the 2 - mercaptoethanol does not accumulate in the cells , and it escapes to the irrigation solution and reacts with the cystine . thus , 2 - mercaptoethanol is continuously taken up by the cells in the form of the mixed disulfide with cystine and is returned to the irrigation solution in is reduced form . with the aid of this cyclic action of 2 - mercaptoethanol , the cells are able to utilize cystine constantly . ( 5 ) a sodium bicarbonate buffer system is important in intracellular fluid to help maintain intercellular ph , fluid movement , corneal deturgesence , and membrane potential difference across mammalian cells , such as the corneal endothelium . various modifications can be made to the present invention without departing from the apparent scope thereof .
an additive for intraocular irrigation solution or surgical solution which provides the anterior chamber and posterior chamber of the eye with protection during surgical procedures that require irrigation . the additive for the solutions is composed of a balanced salt solution containing dextrose supplemented with chondroitin sulfate . other chemical compositions can supplement the additive .