On the calcium concentration of cataractous and normal human lenses and protein fractions of cataractous lenses

doi:10.1016/0014-4835(76)90131-7

Experimental Eye Research

Volume 23, Issue 3, September 1976, Pages 325-332

https://doi.org/10.1016/0014-4835(76)90131-7 Get rights and content

Abstract

Calcium concentrations of a large number of cataractous human lenses and nine normal human lenses were measured by atomic absorption spectroscopy. The mean concentration of calcium in cataractous lenses is 2–13 times higher than the mean calcium concentration of the normal lenses. In considering individual lenses, however, a large number of cataractous lenses contain either less or equivalent calcium concentrations than are present in normal lenses.

The Calcium distributions in both the water-soluble and water-insoluble protein fractions isolated from yellow and brown cataracts were also determined. While some aggregate fractions of yellow lenses are calcium rich, no clearcut differences in the mean calcium concentrations of the remaining protein fractions could be established.

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Cited by (45)

Ca2 + and βγ-crystallins: An affair that did not last?
2016, Biochimica et Biophysica Acta - General Subjects
Citation Excerpt :
The regulation of calcium ions in lens fibre cells has been considered an important requisite for the lens transparency (citing a few articles, [17–21]). Alteration in intracellular free calcium concentration with aging (increases from about 9 μM to 15 μM in human lens) and in many age-related cataracts is described in reports scattered over several decades [22–24]. Intracellular Ca2 + concentrations in lenses from various species are summarized in the comprehensive review by Rhodes and Sanderson [25].
During the last three decades, lens β- and γ-crystallins have found a huge number of kin from numerous taxonomical sources. Most of these proteins from invertebrates and microbes have been demonstrated or predicted to bind Ca^2 + involving a distinct double-clamp motif, which is largely degenerated in lens homologues.
The various aspects of transformation of βγ-crystallins from a quintessential Ca^2 +-binding protein into a primarily structural molecule have been reviewed.
In lens members of βγ-crystallins, the residues involved in Ca^2 + binding have diverged considerably from the classical consensus with consequent reduction in their Ca^2 +-binding properties. This evolutionary change is congenial to their new role as robust constituents of lens. The exact functions of the residual affinity for Ca^2 + are yet to be established.
This review highlights the significance of reduction in Ca^2 +-binding ability of the βγ-crystallins for lens physiology and why this residual affinity may be functionally important. This article is part of a Special Issue entitled Crystallin Biochemistry in Health and Disease.
Regulation of sarco/endoplasmic and plasma membrane calcium ATPase gene expression by calcium in cultured human lens epithelial cells
2007, Cell Calcium
Citation Excerpt :
In all human cataractous lenses, total calcium is elevated 3–3000-fold compared to clear human lenses. Calcium induced lens opacity is a well characterized model for cataract [9–11], and may be a valid model since the loss of transparency is associated with elevated calcium levels in human [12–21], rat [22–24] hypoglycemic [25], X-ray [26] and selenite cataracts [27]. Transparency in many of these systems and others is preserved if calcium homeostasis is maintained [24,28–31].
Since Ca²⁺-ATPase is a major determinant of calcium homeostasis in the lens, we examined the expression of Ca²⁺-ATPase by calcium. An immortalized human lens epithelial cell line, HLE B-3, was treated with thapsigargin to inhibit sarco/endoplasmic reticulum Ca²⁺-ATPase (SERCA) releasing calcium from intracellular stores. Isoforms of the plasma membrane Ca²⁺-ATPase (PMCA) and SERCA were quantified by Western blot and quantitative real time reverse transcription polymerase chain reaction. We showed that both PMCA1 and SERCA3 isoform protein and mRNA are upregulated two- to three-fold in thapsigargin-treated HLE B-3 cells in a time and dose-dependent manner. Thapsigargin did not change the protein or mRNA levels of PMCA2, 3, 4 or SERCA2b. Considering the harmful effects of increased intracellular calcium levels, the upregulation of both SERCA and PMCA pumps suggests it is a compensatory mechanism to restore the calcium concentration to the physiological resting level.
Plasma membrane Ca2+-ATPase expression in the human lens
2005, Experimental Eye Research
The focus of the study was to characterize plasma membrane calcium-ATPase pump (PMCA) isoform expression in the human lens and cultured lens epithelial cells as a basis for future studies of calcium homeostasis in the lens. Proteins and mRNA expression were analysed using Western Immunoblotting and reverse transcription polymerase chain reaction (RT-PCR), respectively. Clear human lenses from the Kentucky Lions Eye Bank and an immortalized human lens epithelial cell line (HLE B-3) were used.
RT-PCR products of PMCA1, PMCA2, and PMCA4 primers were detected at 429, 557, and 849 bp, respectively. All these products were identified as PMCA isoforms by sequence analysis. Protein bands at approximately 130, 115, and 135 kDa were detected by Western blot analysis for PMCA1, PMCA2 and PMCA4, respectively. PMCA3 was not detected at protein or mRNA level in any human lens sample or cell culture, but was detected in the rat brain cortex used as a control. Several bands with lower molecular weights, especially for PMCA2, were detected in the epithelial samples and probably represent break down products of PMCA2. No PMCA proteins or breakdown products were detected in the nuclear or cortical fractions from human lenses.
PMCA1, 2, and 4 proteins and mRNAs are expressed in human lens epithelium and cultured epithelial cells; PMCA3 is not. PMCA was not detected at all in the lens fibre cells. The calcium pump must be selectively processed, independent of other membrane proteins such as the Na–K-ATPase pumps, because the distribution of the Na–K-ATPase pump is asymmetrical in the epithelium and present throughout the lens whereas the calcium pumps are not. The findings of this study provide a basis for further studies to examine the role and modulation of PMCA isoforms in calcium homeostasis and in the development of cataract.
Trace elements in lenses of normal Wistar Kyoto rats
2003, Applied Surface Science
Chemical analysis of the element and organic substance at the site of pathological changes due to aging is one of the approaches of cataract research. Time of flight secondary ion mass spectrometry (TOF-SIMS) microscopy is expected to analyze elements and organic substances in the lens. The purpose of the present study is to compare elements and organic substances in the lenses of normal 4-month-old rats with those of normal 15-month-old rats by means of a TOF-SIMS microscope. The present study showed that the concentration of Ca and Fe was significantly higher, and that of Na and Mg was significantly lower in 15-month-old rats than that in 4-month-old rats. No changes were found in the concentration of K. The present study also showed that the equator contained more Ca, Na and Mg than the nucleus; in contrast, the Cu concentration was higher in the nucleus than in the equator. In 15-month-old rats, Mg and Vit. A in the equator and Zn in the nucleus were significantly lower than those in 4-month-old rats. TOF-SIMS microscopy could detect elemental changes in the rat lens with age, and is expected to be useful approach of cataract studies.
Interactions of Ca2+ with sphingomyelin and dihydrosphingomyelin
2002, Biophysical Journal
Citation Excerpt :
Only recently has our work begun to reveal the conformational differences imparted by this critical double bond (Ferguson-Yankey et al., 2000; Li et al., 2002; Talbott et al., 2000). If all of the Ca2+ ions were unbound and distributed uniformly within the volume of the adult human lens, as in a homogeneous solution, the concentration would be 2.6 mM (Duncan and van Heyningen, 1977; Hightower and Reddy, 1982; Jedziniak et al., 1976; Rasi et al., 1992). This concentration is much higher than that of the free calcium, measured electrochemically to be 10 μM in young lenses and between 12 and 20 μM in older lenses (Duncan et al., 1989).
The changes induced by Ca²⁺ on human lens sphingolipids, sphingomyelin (SM), and dihydrosphingomyelin were investigated by infrared spectroscopy. Ca²⁺-concentration-dependent studies of the head group region revealed that, for both sphingolipids, Ca²⁺ partially dehydrates some of the phosphate groups and binds to others. Ca²⁺ affects the interface of each sphingolipid differently. In SM, Ca²⁺ shifts the amide I′ band to frequencies lower than those in dehydrated samples of SM alone. This could be attributed to the direct binding of Ca²⁺ to carbonyl groups and/or strong tightening of interlipid H-bonds to levels beyond those in dehydrated samples of SM only. In contrast, Ca²⁺ induces relatively minor dehydration around the amide groups of dihydrosphingomyelin and a slight enhancement of direct lipid-lipid interactions. Temperature-dependent studies reveal that 0.2 M Ca²⁺ increases the transition temperature T_m from 31.6 ± 1.0°C to 35.7 ± 1.1°C for SM and from 45.5 ± 1.1°C to 48.2 ± 1.0°C for dihydrosphingomyelin. Binding of Ca²⁺ to some phosphate groups remains above T_m. The strength of the interaction is, however, weaker. This allows for the partial rehydration of these moieties. Similarly, above T_m, Ca²⁺-lipid and/or direct inter-lipid interactions are weakened and lead to the rehydration of amide groups.
Element concentrations and cataract: An experimental animal model
2001, Journal of Trace Elements in Medicine and Biology
The determination of inorganic ions in cataractous human lenses has been the subject of several investigations; nevertheless, few studies have been concerned with trace element contents in lenses, and data are sometimes contradictory. An animal experimental model of induced cataract is here proposed with the aim of evaluating the changes of Ca, Na, K, Cu and Zn concentrations. The cataract was produced by an Nd: YAG Laser treatment of the right eye of sexteen male rabbits. The determination of the elements was performed by atomic absorption spectrometry (both flame and flameless methods) after an acid digestion of samples. Compared with the results obtained in left lenses used as a control (Ca 14.4±5.7 mg/kg d.w.; Na 1.3±0.5 g/kg d.w.; K 9.9±1.1 g/kg d.w.; Cu 0.24±0.09 mg/kg d.w.; Zn 24.8±2.3 mg/kg d.w.), the mean concentration values of opaque lenses showed some significant changes for Ca, Na, and Cu (Ca 123.7±106.6 mg/kg d.w.; Na 4.5±4.3 g/kg d.w; Cu 0.43±0.21 mg/kg d.w.). Potassium showed a tendency to decrease, and zinc to increase. Positive correlations were found between calcium and sodium both in controls (r=0.73, p<0.001) and in treated lenses (r=0.87, p< 0.0001). An inverse correlation between Ca and K confirmed the tendency of potassium to decrease.

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^†: AAS calcium measurements performed by D. F. N.

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Experimental Eye Research

Abstract

References (17)

On the presence and formation of heavy molecular weight aggregates in human normal and cataractous lenses

Exp. Eye Res.

Role of Calcium in Senile Cataract

Biochem. J.

Kalkablagerungen in der Lense

Arch. f. Augenh.

La teneur en calcium du cristallin normal et pathologique

Compt. Rend. Soc. de Biol.

Calcium-induced aggregation of Bovine lens α-crystallin

Invest. Ophthalmol.

Die polarisationsmikroskopische untersuchung der kataraktos getrubten linse

Arch. f. Ophth.

Kristallbildungen in der vorderun augenkammer und linse

Ztschr. f. Augenh.

Cited by (45)

Ca<sup>2 +</sup> and βγ-crystallins: An affair that did not last?

Regulation of sarco/endoplasmic and plasma membrane calcium ATPase gene expression by calcium in cultured human lens epithelial cells

Plasma membrane Ca<sup>2+</sup>-ATPase expression in the human lens

Trace elements in lenses of normal Wistar Kyoto rats

Interactions of Ca<sup>2+</sup> with sphingomyelin and dihydrosphingomyelin

Element concentrations and cataract: An experimental animal model