Profile of polyamines during sprouting and growth of saffron (Crocus sativus L.) Corms

The profile of free and conjugated polyamines putrescine, spermidine, and spermine was studied at the onset of sprouting and during various stages of vegetative growth in saffron (Crocus sativus L.) corms. Polyamines were extracted from the shoot meristems and estimated by high performance liquid chromatography. Free putrescine was not detected at the onset of sprouting, whereas free spermidine and spermine levels increased rapidly on sprouting and decreased during further stages of corm development. The levels of conjugated polyamines were several times higher than the free forms indicating their possible role in the developmental processes. A comparison of polyamine levels of vegetative and floral corms showed higher titers of free polyamines in vegetative and conjugated polyamines in floral corms.     

Polyamines,floral induction and floral development of strawberry (Fragaria ananassa Duch.)

In the short-day plant, strawberry (Fragaria ananassa Duch.), polyamines (putrescine, spermidine and spermine), conjugated spermidine (water-insoluble compounds) and bound amines (putrescine, spermidine, phenylethylamine, 3-hydroxy, 4-methoxyphenylethylamine) accumulated in the shoot tips during floral induction and before floral emergence. Different associations of free amines and conjugated amines were observed during floral induction, as compared with the reproductive phase. During the whole period of floral development, phenylethylamine (an aromatic amine) was the predominant amine, representing 80 to 90% of the total free amine pool. Phenylethylamine conjugates (water-insoluble compounds) were the predominant amides observed prior to fertilization. These substances decreased drastically after fertilization. In vegetative shoot tips from plants grown continously under long days, free polyamines (putrescine, spermidine) and bound polyamines (putrescine, spermidine) were low and no change was observed. Free amines (spermine and phenylethylamine), bound aromatic amines (phenylethylamine, 3-hydroxy, 4-methoxyphenylethylamine), conjugated spermidine and phenylethylamine did not appear. Male-sterile flowers were distinguished by their lack of conjugated spermidine and phenylethyalamine and by a decrease in free phenylethylamine. In normal and sterile strawberry plants -DL-difluoromethylornithine (DFMO), a specific irreversible inhibitor of ornithine decarboxylase (ODC), caused inhibition of flowering and free and polyamine conjugates. When putrescine was added, polyamine titers and flowering were restored. A similar treatment with -DL-difluoromethylarginine (DFMA), a specific, irreversible inhibitor of arginine decarboxylase (ADC), did not affect flowering and polyamine titers. These results suggest that ornithine decarboxylase (ODC) and polyamines are involved in regulating floral initiation in strawberry. The relationship between polyamines, aromatic amines, conjugates, floral initiation and male sterility is discussed.Abbreviations ADC arginine decarboxylase - ODC ornithine decarboxylase - DFMA -DL-difluoromethylarginine - DFMO -DL-difluoromethylornithine - Put putrescine - Spd spermidine - Spm spermine - Phen phenylethylamine - 3H4M Phen 3-hydroxy, 4-methoxyphenylethylamine     

Floral initiation in Rudbeckia hirta (Asteraceae) under limited inductive photoperiodic treatments

Two experiments were conducted to examine the response of Rudbeckia hirta to limited inductive photoperiodic treatments. The first examined the effects on plants grown to an thesis of the second axillary inflorescence, and the second examined the early histological events within the meristem. Plants of Rudbeckia hirta were grown to maturity under short days (SD). At maturity, half the plants were placed in long days (LD). In the first experiment, the plants remained under LD for 0, 8, 16, 24, or 32 days before being returned to SD with an additional group remaining under LD as a control. In the second experiment, the plants remained under LD for 0, 4, 8, 12, 16, 20, 24, or 28 days before being returned to SD. Meristems were sampled 0, 4, 8, or 12 days after return to SD and histologically examined. Four groups of plants receiving 32, 36, 40, or 44 LD were used as a continuous LD control. When grown to anthesis, plant height and branch number increased as the number of inductive cycles increased. Plants receiving 24 or more LD reached anthesis earlier than plants receiving fewer LD. Histological examination of plants receiving only 4 LD showed they never progressed beyond early floral initiation. After 12 LD, the meristems continued to develop even when returned to SD, indicating that enough of the floral stimulus had reached the meristem to initiate flowering. Once involucral bract primordia initiated, floral development continued whether in LD or SD conditions.     

Tissue-specific changes in polyamine levels of neural tissue and fat body in adult crickets

The three major polyamines—putrescine, spermidine, and spermine—were studied and changes of their levels were examined in extracts of cerebral ganglia and fat body from adult Acheta domesticus. In nervous tissue, only spermidine and spermine were present and spermine was two- to three-fold more abundant than spermidine. The polyamine levels were high up to day 3, decreased on day 4, and then remained relatively unchanged up to day 10. The spermidine/spermine ratios decreased during the imaginal life. Higher spermidine titres were observed in the neural tissue of egg-laying females compared to virgin females. In the fat body, putrescine was detected together with spermidine and spermine. Spermidine and spermine levels were two-fold higher than putrescine. Fat body of virgin females contained two times more polyamines than male fat body. Low at emergence, spermidine and spermine concentrations peaked on days 2–3 only in females, and egg-laying was characterized by an increase of putrescine and spermidine titres. Starvation did not change polyamine contents, implying homeostatic regulation of the intracellular polyamine metabolism. These data showing tissue specific changes in polyamine levels during the imaginal life of Acheta domesticus point to the physiological importance of polyamines as possible intracellular regulators during adult insect development. © 1993 Wiley-Liss, Inc.     

Free and conjugated polyamines during de novo floral and vegetative bud formation in thin cell layers of tobacco

The concentrations of three classes of polyamines, trichloroacetic acid-soluble (free), TCA-soluble conjugated (to small molecules) and TCA-insoluble conjugated (to macromolecules), was examined during de novo floral and vegetative bud formation in thin cell layers of Nicotiana tabacum L. cv. Samsun. Explants (consisting of 5–6 layers of epidermal, subepidermal and parenchyma cells) were excised either from floral pedicels or from stem internodes at the unripe fruit stage and cultured on the same medium. In the former, the first de novo formed flower buds appeared on day 8 of culture, while in the latter the first vegetative domes appeared on day 10. In both cases the number of floral and vegetative buds increased up to day 12 and 15, respectively. Changes in dry weight were determined throughout the culture period. Free and conjugated putrescine titer increased 5–60 times in both types of culture and in the three classes of polyamines examined; spermidine content also increased, while spermine, when present, did not show significant changes. TCA-soluble conjugated polyamines were most abundant, being about 2-fold the TCA-insoluble conjugated ones and 10-fold the free ones. The major increment in putrescine and spermidine content occurred in stem internode explants developing vegetative buds. In pedicel explants the maximum putrescine level was reached before or on day 8 in culture (emergence of the first flower buds with calyx initials), while in stem internode explants the maximum level was reached on day 12, at the emergence of the first vegetative buds with leaf primordia. While spermidine prevailed on day 0, putrescine was the most abundant polyamine during both differentiation processes. The putrescine content rapidly increased immediately after the onset of culture. Thus conjugated polyamines, especially putrescine, and not only the free ones, seem to be involved in both the reproductive and vegetative phases of tobacco growth and development.     

Changes in polyamine pattern are involved in floral initiation and development in Polianthes tuberosa

In the day-neutral plant Polianthes tuberosa (cv. Double) putrescine and spermine in corms at the early floral initiation stage decreased by 26 and 36%, respectively, compared with that in the vegetative stage. In contrast, a sharp increase in spermidine and cadaverine titers in corms was recorded at the early floral initiation stage. However, cadaverine in corms disappeared at the flower development stage. Polyamines in the roots were generally lower than those in the leaves and corms. In no case was the change in endogenous polyamine titers in the roots and leaves associated with floral initiation and flower development in P. tuberosa. Exogenous application of spermidine at 5, 25 or 150 microg per plant at the vegetative stage did not affect flower primordium counts. However, addition of a spermidine synthase inhibitor, cyclohexylamine, at 150 or 250 microg per plant (each dose was applied two times in total at an interval of 4 days) significantly reduced flower primordium counts, indicating that spermidine is involved in floral initiation and floral development in P. tuberosa. In P. tuberosa corms at the vegetative stage arginine decarboxylase activity rises and decreases at the early floral initiation stage. In contrast, ornithine decarboxylase activity reaches the highest level at the early floral initiation stage and declines significantly at the vegetative stage. Results indicate that an increase in spermidine and a transient increase in cadaverine titers in the corms seem characteristic of early floral initiation in P. tuberosa. It is also suggested that a significant reduction in putrescine and spermine in the corms is involved in the early floral initiation in P. tuberosa.     

Polyamine oxidase and tissue transglutaminase activation in rat small intestine by polyamines.

Polyamine degradation was studied in the small intestine from rats fed on a polyamine-supplemented diet. Lactalbumin diet was given to Hooded-Lister rats, with or without 5 mg rat(-1) day(-1) of putrescine or spermidine for 5 days. Polyamine oxidase activity increased with putrescine and spermidine in the diet, whereas spermidine/spermine N(1)-acetyltransferase and diamine oxidase activities were unchanged. We also studied the calcium-dependent and -independent tissue transglutaminase activities, since they can modulate intestinal polyamine levels. Both types of enzymes increased in the cytosolic fraction after putrescine (about 65%) or spermidine (80-100%). Our results indicate that exogenous polyamines stimulate intestinal polyamine oxidase and tissue transglutaminase activities, probably to prevent polyamine accumulation, when other pathways of polyamine catabolism (acetylation and terminal catabolism) are not activated.     

Polyamine metabolism,floral initiation and floral development in Chrysanthemum (Chrysanthemum morifolium Ramat.)

In the short-day plant Chrysanthemum (Chrysanthemum morifolium Ramat. variety Pavo) putrescine and spermidine conjugates appeared in the apical bud before the first observable transformation of the meristem into floral structures. These compounds accumulated on floral initiation and well before floral evocation. Spermidine conjugates were predominant during floral initiation whereas free amines did not accumulate to any significant extent. Different associations of amides were observed during floral initiation as compared with the reproductive phase. 3,4-Dimethoxyphenethylamine conjugates (water-insoluble compounds) were the predominant amine conjugates observed during flower development. These compounds decreased drastically after fertilization. In vegetative buds from plants grown in long days polyamine conjugates were very low and appeared as plants aged. We present evidence that ornithine decarboxylase (ODC) regulates putrescine biosynthesis during floral initiation and floral development. When ODC action was blocked by DFMO (-DL-difluoromethylornithine, a specific, irreversible inhibitor of ODC), flowering was inhibited, and free and conjugated polyamines were not detected. This treatment led to a slight enhancement of ADC activity. When putrescine was added, polyamine titers and flowering were restored. A similar treatment with DFMA (-DL difluoromethylarginine, a specific, irreversible inhibitor of ADC) did not affect flowering and the polyamine titers. The results suggest that ODC and polyamine conjugates are involved in regulating floral initiation in Chrysanthemum.Abbreviations ADC arginine decarboxylase - ODC ornithine decarboxylase - DFMA -DL-difluoromethylarginine - DFMO -DL-difluoromethylornithine     

水稻胚与胚乳分化发育中的内源多胺

稻胚发育过程中,其内源多胺以腐胺、亚精胺为主。在幼胚分化期,腐胺和亚精胺的含量很高;幼胚分化完成时,其含量急剧下降;直至分化后期才趋稳定。在胚及胚乳发育时期,还出现一种未知多胺X_(22),其含量除在胚分化完成时较少外,在胚发育的其他各期中,含量则一直很高。DNA和蛋白质含量的变化,从分化期开始递增直至物质积累成熟期,其趋势均相同。多胺可能参与胚与胚乳中核酸和蛋白质合成的调节。     

Levels of polyamines and kinetic characterization of their uptake in the soybean pathogen Phytophthora sojae

Polyamines are ubiquitous biologically active aliphatic cations that are at least transiently available in the soil from decaying organic matter. Our objectives in this study were to characterize polyamine uptake kinetics in Phytophthora sojae zoospores and to quantify endogenous polyamines in hyphae, zoospores, and soybean roots. Zoospores contained 10 times more free putrescine than spermidine, while hyphae contained only 4 times as much free putrescine as spermidine. Zoospores contained no conjugated putrescine, but conjugated spermidine was present. Hyphae contained both conjugated putrescine and spermidine at levels comparable to the hyphal free putrescine and spermidine levels. In soybean roots, cadaverine was the most abundant polyamine, but only putrescine efflux was detected. The selective efflux of putrescine suggests that the regulation of polyamine availability is part of the overall plant strategy to influence microbial growth in the rhizosphere. In zoospores, uptake experiments with [1,4-(14)C]putrescine and [1,4-(14)C]spermidine confirmed the existence of high-affinity polyamine transport for both polyamines. Putrescine uptake was reduced by high levels of exogenous spermidine, but spermidine uptake was not reduced by exogenous putrescine. These observations suggest that P. sojae zoospores express at least two high-affinity polyamine transporters, one that is spermidine specific and a second that is putrescine specific or putrescine preferential. Disruption of polyamine uptake or metabolism has major effects on a wide range of cellular activities in other organisms and has been proposed as a potential control strategy for Phytophthora. Inhibition of polyamine uptake may be a means of reducing the fitness of the zoospore along with subsequent developmental stages that precede infection.     

Levels of Polyamines and Kinetic Characterization of Their Uptake in the Soybean Pathogen Phytophthora sojae

Polyamines are ubiquitous biologically active aliphatic cations that are at least transiently available in the soil from decaying organic matter. Our objectives in this study were to characterize polyamine uptake kinetics in Phytophthora sojae zoospores and to quantify endogenous polyamines in hyphae, zoospores, and soybean roots. Zoospores contained 10 times more free putrescine than spermidine, while hyphae contained only 4 times as much free putrescine as spermidine. Zoospores contained no conjugated putrescine, but conjugated spermidine was present. Hyphae contained both conjugated putrescine and spermidine at levels comparable to the hyphal free putrescine and spermidine levels. In soybean roots, cadaverine was the most abundant polyamine, but only putrescine efflux was detected. The selective efflux of putrescine suggests that the regulation of polyamine availability is part of the overall plant strategy to influence microbial growth in the rhizosphere. In zoospores, uptake experiments with [1,4-¹⁴C]putrescine and [1,4-¹⁴C]spermidine confirmed the existence of high-affinity polyamine transport for both polyamines. Putrescine uptake was reduced by high levels of exogenous spermidine, but spermidine uptake was not reduced by exogenous putrescine. These observations suggest that P. sojae zoospores express at least two high-affinity polyamine transporters, one that is spermidine specific and a second that is putrescine specific or putrescine preferential. Disruption of polyamine uptake or metabolism has major effects on a wide range of cellular activities in other organisms and has been proposed as a potential control strategy for Phytophthora. Inhibition of polyamine uptake may be a means of reducing the fitness of the zoospore along with subsequent developmental stages that precede infection.     

Effects of inhibitors of ornithine and S-adenosylmethionine decarboxylases on L6 myoblast proliferation

The role of polyamines in myoblast proliferation was studied by treating cells of Yaffe's L6 line of rat myoblasts with inhibitors of polyamine synthesis. Both an irreversible inhibitor of ornithine decarboxylase--difluoromethyl-ornithine (DFMO)--and a competitive inhibitor of S-adenosyl-methionine decarboxylase--methylglyoxal-bis(guanylhydrazone) (MGBG)--depressed spermidine levels and inhibited myoblast proliferation. Spermine levels were not significantly depressed by either inhibitor and putrescine levels were decreased only by DFMO. Putrescine and spermidine, but not magnesium, prevented inhibition of myoblast proliferation by DFMO and MGBG; determination of 14C-DFMO uptake in the presence and absence of these compounds demonstrated that they did not reduce the rate or extent of inhibitor uptake and thus prevent its inhibition of ornithine decarboxylase. Thus it seems likely that these inhibitors reduce cell proliferation by inhibiting polyamine formation. Addition of spermidine to the cells led to a substantial reduction in the activity of S-adenosyl-methionine-decarboxylase, suggesting that the enzyme is subject to negative regulation by the products of the polyamine biosynthetic pathway. Unexpectedly, addition of spermidine also increased intracellular putrescine levels; this apparently resulted from conversion of spermidine to putrescine. Addition of putrescine or spermidine in the absence of serum did not increase the rate of myoblast proliferation although it did elevate intracellular polyamine levels as expected. We conclude that some threshold level of one or more polyamines (probably spermidine) is necessary but not sufficient for initiation and maintenance of myoblast proliferation in culture.     

A specific role for spermidine in the initiation phase of somatic embryogenesis in Panax ginseng CA Meyer

Somatic embryogenesis of Panax ginseng CA Meyer was initiated from suspension aggregates of an embryogenic callus, in a liquid medium consisting of half strength Murashige and Skoog (1962) supplemented with the synthetic auxin benzoselenienyl-3 acetic acid. The addition of spermidine to this initiation medium significantly increased the production of somatic embryos. In this case, the total polyamine content of the embryogenic mass was higher than that of cultures without spermidine. At day 6 of the culture, a transient accumulation of free polyamines, mainly spermidine, was observed. After this peak, free and conjugated polyamines levels did not show significant variation nor did the polyamine oxidase activity. The results clearly demonstrated that spermidine supplied to the medium was oxidised by polyamine oxidase and partially metabolised into putrescine. The role of spermidine and its interaction with auxin in the initiation of the embryogenic process in Panax ginseng are discussed in relation to embryogenic potential.     

Polyamine levels and tomato fruit development: possible interaction with ethylene

Fruits of tomato, Lycopersicon esculentum Mill. cv Liberty, ripen slowly and have a prolonged keeping quality. Ethylene production and the levels of polyamines in pericarp of cv Liberty, Pik Red, and Rutgers were measured in relation to fruit development. Depending on the stage of fruit development, Liberty produced between 16 and 38% of the ethylene produced by Pik Red and Rutgers. The polyamines putrescine, spermidine, and spermine were present in all cultivars. Cadaverine was detected only in Rutgers. Levels of putrescine and spermidine declined between the immature and mature green stages of development and prior to the onset of climacteric ethylene production. In Pik Red and Rutgers, the decline persisted, whereas in Liberty, the putrescine level increased during ripening. Ripe pericarp of Liberty contained about three and six times more free (unconjugated) polyamines than Pik Red and Rutgers, respectively. No pronounced changes in spermidine or cadaverine occurred during ripening. The increase in the free polyamine level in ripe pericarp of Liberty may account for the reduction of climacteric ethylene production, and prolonged storage life.     

Polyamine changes during the development of zygotic embryos in Prunus avium

A study of the polyamine profile was carried out during zygotic embryo development in Prunus avium. Zygotic embryos were collected from 2 donor trees and sorted into 3 size classes: C1 [2.5 to 3.5 mm]; C2 [3.6 to 4.5 mm] and C3 [5.5 to 7 mm]. Evolution of the various polyamines was similar for the two donor trees. Changes in the relative amount of the various free polyamines were observed during zygotic embryo development. Agmatine and spermine levels increased from C1 to C3. Spermidine, the predominant polyamine, showed a two-fold decrease in C3 compared with C1 and C2; the evolution of putrescine was opposed, showing an increase in the last developmental stage. The putrescine/spermidine ratio could be a marker for these 3 developmental stages with a higher ratio in C3 compared with C1 and C2. Polyamine changes in cotyledons from class C1 were investigated during in vitro culture. A 10-day induction on a medium containing 2,4-dichlorophenoxyacetic acid (2,4-D) and kinetin caused a strong decline in free spermidine levels and a dramatic increase in free putrescine. The formation of conjugated putrescine occurred simultaneously, and twenty days after removal of growth regulators, the various polyamine contents were still at the same level.Abbreviations Agm agmatine - Dap diaminopropane - 2,4-D 2,4-dichlorophenoxyacetic acid - Put putrescine - Spd spermidine - Spm spermine     

Polyamine biosynthesis in the developing rabbit palate

Levels of putrescine, spermidine, and spermine and their biosynthetic enzymes, ornithine decarboxylase (ODC) and S-adenosylmethionine decarboxylase (SAMDC) were measured in the developing rabbit palate between day 14 and day 18 of gestation. DNA, RNA, and protein synthesis were also measured during this time period to determine if a correlation exists between polyamine biogenesis and macromolecular synthesis. ODC activity was found to be twice as high on day 14 as on the succeeding days of gestation, while SAMDC activity did not change significantly. Levels of putrescine and spermine were higher on day 14 by 22% and 30%, respectively, than levels on day 18. Spermidine concentration did not change. DNA synthesis remained relatively constant between days 14 and 18 of gestation, suggesting that there is no peak in cell proliferation during this period. RNA synthesis was elevated significantly on day 14 and protein synthesis was significantly higher on both days 14 and 16. This data indicates that there is no correlation between polyamine synthesis and cell proliferation during this period of palatal development, but polyamines could play a regulatory role in RNA and/or protein synthesis.     

Polyamines and their biosynthetic enzymes in Ehrlich ascites-carcinoma cells. Modification of tumour polyamine pattern by diamines.

1. Ehrlich ascites-carcinoma cells contained relatively high concentrations of spermidine and spermine, but the putrescine content of the washed cells was less than 10% of that of higher polyamines. 2. Ascites-tumour cells likewise exhibited high activities of L-ornithine decarboxylase (EC 4.1.1.17), S-adenosyl-L-methionine decarboxylase (EC 4.1.1.50), spermidine synthase (EC 2.5.1.16) and spermine synthase. 3. During the first days after the inoculation, the polyamine pattern of the ascites cells was characterized by a high molar ratio of spermidine to spermine, which markedly decreased on aging of the cells. 4. Various diamines injected into mice bearing ascites cells rapidly and powerfully decreased ornithine decarboxylase activity in the carcinoma cells, apparently through a mechanism that was not a direct inhibition of the enzyme in vitro. Cadaverine (1,5-diaminopentane) and 1,6-diaminohexane were the most potent inhibitors of ornithine decarboxylase among the amines tested. 5. Chronic treatment of the mice with diamines resulted in a virtually complete disappearance of ornithine decarboxylase activity, and after 24h a significant decline in spermidine accumulation. 6. Cadaverine appeared to be an especially suitable compound for use as an inhibitor of the synthesis of higher polyamines, at least in Ehrlich ascites cells, since this diamine also acted as a competitive inhibitor for putrescine in the spermidine synthase reaction without being incorporated into the higher polyamines.     

Changes in endogenous polyamine levels are associated with differentiation in Dictyostelium discoideum.

This is the first report correlating levels of polyamines and its fractions with differentiation in Dictyostelium discoideum. Temporal changes in endogenous levels of free, conjugated and bound putrescine, spermidine and spermine were analysed at critical stages of morphogenesis in this organism. No spermine was found at any given stage and putrescine was the most abundant polyamine. There was a sharp increase in the levels of both free (and total) and conjugated forms of putrescine and spermidine at the slug stage as compared to the growth phase. The levels of putrescine and spermidine were found to be higher in isolated prespore cells as compared to the prestalk cells. Remarkably, the levels of polyamine decreased at the early culminant stage. Data suggest that a moderate level of polyamines is needed for growth but it is important to have high levels of polyamines at the time of differentiation.     

Cellular content and biosynthesis of polyamines during rooster spermatogenesis.

The natural polyamines spermine and spermidine, and the diamine putrescine, were extracted from rooster testis cells separated by sedimentation at unit gravity, and from vas-deferens spermatozoa. The ratios spermine/DNA and spermidine/DNA were kept relatively constant throughout spermatogenesis, whereas the ratio putrescine/DNA rose in elongated spermatids. The cellular content of spermine, spermidine and putrescine decreased markedly in mature spermatozoa. Two rate-limiting enzymes in the biosynthetic pathway of polyamines, ornithine decarboxylase and S-adenosyl-L-methionine decarboxylase, showed their highest activities at the end of spermiogenesis and were not detectable in vas-deferens spermatozoa. A marked reduction in cell volume during spermiogenesis without a parallel decrease in the cellular content of polyamines suggests the possibility that the marked changes in chromatin composition and structure occurring in rooster late spermatids could take place in an ambience of high polyamine concentration.     

Active transport and metabolic characteristics of polyamines in the rat lens

Putrescine, spermidine and spermine were transported into the rat lens against a concentration gradient. This process appeared to be energy-dependent and involved a carrier system different from those for amino acids. Competition experiments suggested that the three polyamines were transported by the same system or very similar systems. Incorporated spermine was converted to spermidine and putrescine, and spermidine was converted to putrescine. In contrast, the conversion of putrescine to spermidine and spermine, or the conversion of spermidine to spermine was not observed. Furthermore, ornithine was not utilized for the synthesis of putrescine. These metabolic characteristics of the polyamines in the rat lens were correlated with the extremely low activities of ornithine decarboxylase and S-adenosylmethionine decarboxylase. Other enzymes of polyamine metabolisms, however, were relatively active. In conclusion, the lens has a very low ability for the de novo synthesis of polyamines. The polyamines in the lens are considered to be supplied form the surrounding intraocular fluid by an active transport system specific for polyamines.