Effect of p-p'-DDE administered in vivo and in vitro on Ca2+ binding and Ca2+-Mg2+-ATPase activity in egg shell gland mucose of ducks

The Effect of Different Levels of Dietary Magnesium on Eggshell Quality and Laying Hen's Performance

This study aimed to investigate the effects of different levels of dietary magnesium (Mg) on eggshell quality and laying hen's performance. Four dietary treatments including a commercial-type basal diet containing 3.19 g/kg Mg and three additional diets supplemented with 2, 4, or 6 g/kg magnesium oxide (MgO) to provide 4.03, 4.87, or 5.71 g/kg Mg were used in a completely randomized design. A total of 120 Bovans White layers at the age of 35 weeks were fed with dietary treatments for 8 weeks. Results indicated that increasing concentrations of Mg in the diets significantly increased hen-day egg production and feed intake (P < 0.05). Dietary Mg supplementation had no effect on egg weight, feed conversion ratio, and average daily weight gain. Eggshell weight, thickness, and strength were significantly increased by adding Mg to the diets (P < 0.05). Dietary treatments significantly increased yolk weight (P < 0.05) but decreased yolk color (P < 0.05). Albumen weight, Haugh unit, yolk shape, and egg shape index were similar among the dietary treatments. Eggshell Mg content (g/kg of dry matter) was significantly increased by the inclusion of Mg in the diets. In conclusion, the results of this study indicated that supplementation of Mg up to 5.71 g/kg diet improved eggshell quality and laying hen's performance.

The eggshell features and clutch viability of the broad-snouted caiman (Caiman latirostris) are associated with the egg burden of organochlorine compounds

Organochlorine compounds (OCCs) are toxic and have been identified as endocrine-disrupting chemicals (EDCs). The broad-snouted Caiman (Caiman latirostris) is an oviparous species widely distributed in South America with potential to accumulate OCCs. The eggshell is formed during passage of the eggs through the oviduct. Since the oviduct is a target of hormone actions, exposure to OCCs could modify eggshell quality, thus affecting clutch viability. Eight clutches were collected from wetlands of Parana River tributaries, in north-eastern Argentina. Two to four eggs per clutch were used to establish the burden of OCCs, eggshell thickness and eggshell porosity. The remaining eggs were incubated in controlled conditions. Ten days after hatching, hatchling survival was assessed. Organochlorine pesticide residues (OCPs) were found in all clutches, while polychlorinated biphenyls (PCBs) were present in all but one clutch. The principal contributors to the OCP burden were members of the DDT family and oxychlordane. Eggshell thickness was 400.9±6.0 μm and, unexpectedly, no association between eggshell thickness and the OCC burden was found. The number of pores in the outer surface was 25.3±4.3 pores/cm². A significant inverse correlation between porosity and OCC burden was found (Pearson r= -0.81, p= 0.01). Furthermore, a decrease in caiman survival with decreased pore density was observed (Pearson r= 0.73, p= 0.04). Our findings highlight another potential negative impact of current and past use of OCCs on wildlife species.

DDE-induced eggshell thinning in birds: effects of p,p'-DDE on the calcium and prostaglandin metabolism of the eggshell gland

1. The focus of this review is the effects and mechanism of action of p,p'-DDE on eggshell formation in birds. Inhibition of prostaglandin synthesis in the eggshell gland mucosa is a probable mechanism for p,p'-DDE-induced eggshell thinning. 2. The duck is sensitive to p,p'-DDE-induced eggshell thinning but the domestic fowl is not, and studies comparing the two species in regard to the calcium and prostaglandin metabolism of the eggshell gland have shown that eggshell thinning induced by p,p'-DDE in ducks is accompanied by reduced activity of prostaglandin synthetase, reduced levels of prostaglandin E2, and reduced uptake of 45Ca by the eggshell gland mucosa. The content of calcium, bicarbonate, chloride, sodium, and potassium are also reduced in the eggshell gland lumen in ducks exhibiting eggshell thinning. None of these effects are seen in the domestic fowl. 3. Inhibition of prostaglandin synthesis is a specific effect of p,p'-DDE. The detrimental effects of p,p'-DDE on the eggshell gland seem to be unique when comparing the compound with structurally related substances, i.e., similar treatment regimens with o,p'-DDE, p,p'-DDT, o,p'-DDT, and p,p'-DDD do not cause eggshell thinning in ducks. Neither do they inhibit prostaglandin synthesis in the eggshell gland mucosa. 4. Administration of other compounds that do inhibit prostaglandin synthesis, e.g., indomethacin, does cause the same effects as those seen with p,p'-DDE, i.e., eggshell thinning and the described effects on the calcium and prostaglandin metabolism of the eggshell gland.

Inhibition of eggshell formation in domestic fowl by indomethacin: Relation to calcium and prostaglandin metabolism in the eggshell gland mucosa

1. The involvement of prostaglandins in eggshell formation in the domestic fowl was investigated by considering the effects of the drug indomethacin on the calcium metabolism on the eggshell gland. Egglaying birds were given a single dose (100 mg) of indomethacin at the beginning of shell calcification. Fourteen hours later the birds were sacrificed and the effects of the drug were determined. There was a 21% reduction in the shell thickness of the egg present in the shell gland at the time of slaughter (P < 0.01). The calcium content of the eggshell gland mucosa was increased to 153% (P < 0.01) of the controls. In the treated birds, there was 43% more calcium (P < 0.05) present in the shell gland lumen (recovered by rinsing with Tris buffer) than in the gland lumen of control birds. Total calcium in blood plasma was decreased by 15% (P < 0.05). In homogenate and three subcellular fractions (MIII, FI and FIII) of eggshell gland mucosa, 45Ca uptake was significantly reduced (i.e. by 29%, 25%, 17% and 35%, respectively). A significant reduction (62-66%) was also observed in the synthesis of PGF2 alpha, PGE2 and TxB2 by eggshell gland mucosa homogenate. 2. The effects of indomethacin treatment on the calcium metabolism of the avian eggshell gland are discussed and compared with p,p-DDE-induced alterations in calcium metabolism and prostaglandin synthesis by the eggshell gland.

Immunohistochemical localization of a calcium pump and calbindin-D28k in the oviduct of the laying hen

The localization of a plasma membrane calcium pump in the oviduct of the laying hen was investigated by immunohistochemical techniques, utilizing a monoclonal antibody (5F10) produced against the human erythrocyte calcium pump. This antibody was shown to react with an epitope of the pump in oviductal tissue, and prominent staining was observed on the microvilli of the tubular gland cells of the hen shell gland (uterus) and the isthmus. The Ca2+ pump was not detectable in the infundibulum or the magnum. Calbindin-D28k, also localized by immunohistochemical means, was observed to be present in the tubular gland cells of the shell gland and the distal isthmus (adjacent to shell gland) but not in either the proximal isthmus (adjacent to the magnum), the magnum or the infundibulum. The localization of the Ca2+ pump in the oviduct corresponds to known sites of mineral deposition during egg shell formation. The distribution of calbindin-D28k differed, co-localizing with the Ca2+ pump in the shell gland and distal isthmus but not in the proximal isthmus. This might reflect a greater rate of active Ca2+ secretion in the distal isthmus and shell gland as compared to the proximal isthmus.

Role of magnesium in egg shell formation in the domestic hen

1. The effects of feeding diets containing various amounts of magnesium on plasma concentration of calcium and magnesium in the domestic hen were investigated. 2. Plasma concentrations of calcium and magnesium decreased during shell formation in all birds. 3. Plasma magnesium content and egg shell thickness were severely reduced in birds given diets containing either 207 or 132 mg Mg++/kg. 4. Using electron microscopy, a precise correlation was observed between the normal distributions of magnesium and organic material across the egg shell of the domestic hen.

Histochemical studies of Ca-ATPase, succinate and NAD+-dependent isocitrate dehydrogenases in the shell gland of laying Japanese quails: with special reference to calcium-transporting cells

In order to elucidate the problem of which cells are involved in calcium transport and to estimate the role of mitochondria in calcium transport in the avian shell gland, the fine structure and the Ca-ATPase, succinate dehydrogenase (SDH) and nicotinamide adenine dinucleotide (NAD+)-dependent isocitrate dehydrogenase (NAD+-ICDH) activity of the shell gland of egg-laying Japanese quails were examined. The surface epithelial cells, consisting of ciliated cells with cilia and microvilli and non-ciliated cells with microvilli, had many large and electron-dense granules. The tubular-gland cells occupied the proprial layer and lacked secretory granules. When an egg was in the shell gland, the well-developed mitochondria of tubular-gland cells characteristically tended to accumulate in the apical cytoplasm, while they were scattered throughout the cytoplasm when an egg was not in the shell gland. Intense Ca-ATPase activity was found on the microvilli of tubular-gland cells, and moderate activity was found on the lateral-cell surface. In the surface epithelial cells, the basolateral cell surface showed moderate enzymatic activity. Both SDH and NAD+-ICDH activity were found in tubular-gland cells when an egg was in the shell gland. These results strongly suggest that calcium for eggshell calcification is actively transported by the tubular-gland (depending on Ca-ATPase activity) and that the mitochondria of gland cells may play an important role in this process as an energy source.

Relation between Ca metabolism and ATPase activities in the subcellular fractions from duck eggshell gland mucosa after DDE administration during different stages of eggshell formation

The ATP-dependent Ca2+ uptake by and the Ca2+-Mg2+-activated ATPase activity in the subcellular fractions from the eggshell gland of two varieties of ducks, Indian Runner ducks (IRD) and the cross-breed of Swedish and Rouen ducks (SRD), showed functional changes during eggshell formation in relation to the values in the resting state. DDE inhibited the Ca2+ uptake (Ca) but increased the Ca2+-Mg2+-ATPase activity (P) of fractions from active but not of those from resting glands. DDE reduced the Ca/P ratio of several fractions from active glands. DDE inhibited the functional increase in Ca2+-Mg2+-ATPase in the IRD homogenate, however. The effect of DDE on the eggshell index of mature eggshell was greater in IRD than in SRD, the reason for this being that the effect was exerted during a shorter time period in the latter variety.

Relation between Ca2+ uptake and ATPase activity in the particulate fractions of the eggshell gland mucosa of the domestic fowl and duck

The relation between the rates of ATP-dependent Ca2+ uptake and ATP hydrolysis was studied in homogenates of eggshell gland mucosa and its subcellular fractions from the domestic fowl and duck. The Ca2+-Mg2+-ATPase activity was 5-10% of that of the "basal" Mg2+-ATPase at an optimal Ca2+ concentration in the subfractions. The presence of K+ and/or Na+ increased the rate of Ca2+ uptake and the Ca2+-Mg2+-ATPase activity; the effects of K+-Na+ were not inhibited by ouabain. The Ca/P ratio varied with the experimental conditions. At 10(-4) M Ca2+ and in the absence of K+ Na+ it was 0.8, and in their presence 0.4.

Comparison of the effect of DDE on the Ca metabolism of the eggshell gland and its subcellular fractions of the duck and the domestic fowl

In a strain of ducks sensitive to the eggshell-thinning effect of p-p'-DDE, administration of 40 mg kg of the compound in the food for 45 days reduced the eggshell index (EI) by 13% and the content of calcium in the fluid of the shell gland forming an eggshell by 36%, and raised the calcium content of the shell gland mucosa by 19%, compared with the control values. DDE inhibited the translocation (secretion) of calcium between the gland mucosa and the uterine cavity. The ATP-dependent binding of Ca2+ to the subcellular fractions of the gland mucosa was reduced in DDE-treated ducks. The Ca2+ binding to a microsomal subfraction (FI) rich in fragments of the plasma membrane was reduced by 16%, whereas that to a subfraction FIII which bound Ca2+ at a very high rate was reduced by 36%. The latter may contain calcium-secreting granules of the gland. In the mitochondrial fraction the Ca2+ binding was reduced by 35%. In the domestic fowl DDE did not lower EI or interfered with the translocation of calcium between the shell gland mucosa and uterine cavity. DDE administration increased the Ca2+ binding to FI by 26%; the binding to other subfractions was not changed significantly. DDE may interfere with the stimulus-secretion mechanism of the eggshell gland in ducks through its effect on Ca2+ binding.

Effect of DDE on the Ca metabolism of the duck eggshell gland and its subcellular fractions; relation to the functional stage

Administration of DDE to Indian Runner ducks (Anas platyrhynchos var.) reduced the eggshell index by 28% and the calcium content of the secreted fluid in the shell gland by 25%. DDE inhibited the functional decrease of the calcium content of the gland cells that occurred during eggshell formation. DDE reduced the functional increase in the ATP-dependent binding of Ca2+ to a microsomal subfraction FIII prepared from Ca-secreting glands forming an eggshell. In subfraction FI the Ca2+ binding was decreased by DDE even when the gland contained a mature shell. FIII probably contained calcium-secreting granules, whereas FI contained plasma membrane fragments of the gland cells.

The inhibitory effect of some chlorinated hydrocarbon pesticides on the ATP-dependent Ca2+ binding of the particulate fraction of the eggshell gland mucosa cells

The pesticide p-p'-DDT and its persistent metabolite p-p'-DDE cause thinning of the eggshells in several species of birds. In earlier investigations on ducks this thinning was found to be associated with a reduction of the ATP-dependent Ca2+ binding to a homogenate of the shell gland mucosal cells by DDE. The activity of a Ca2+-Mg2+-activated ATPase in the homogenate was also decreased on administration of DDE in vivo. We have therefore investigated the in vitro effects of some other chlorinated hydrocarbon pesticides of ecotoxicological interest on the ATP-dependent Ca2+ binding and the Ca2+-Mg2+-activated ATPase activity in a homogenate of the eggshell gland mucosa of the hen and determined the molar concentrations that produced 50% inhibition (=IC50). Several of the investigated compounds, namely toxaphene, chlordane, p-p'-DDD, o-p'-DDE, p-p'-DDT, methoxychlor and PCB (Arochlor 1242), had a similar IC50 to inhibit the Ca2+ binding as p-p'-DDE. Lindane, p-p'-DDA and biphenyl had an IC50 3.3-4 times higher and that of 2.4 D was 13.5 times higher than that of p-p'-DDE. When the IC50 of some of the compounds (p-p'-DDE, PCB, toxaphene, Lindane) was determined that decreased the Ca2+-Mg2+-activated ATPase of the homogenate it was found to be only 18 to 29 per cent of that needed to inhibit the Ca2+ binding by the homogenate. It is therefore probable that some other effect than inhibition of this enzyme is also involved in the Ca2+-binding process and affected by the compounds.