Low Calcium Environment Research Articles

Calcium regulates the mycophagous ability of Burkholderia gladioli strain NGJ1 in a type III secretion system-dependent manner

BackgroundA rice associated bacterium Burkholderia gladioli strain NGJ1 demonstrates mycophagy, a phenomenon wherein bacteria feed on fungi. Previously, we have reported that NGJ1 utilizes type III secretion system (T3SS) to deliver a prophage tail-like protein (Bg_9562) into fungal cells to establish mycophagy.ResultsIn this study, we report that calcium ion concentration influences the mycophagous ability of NGJ1 on Rhizoctonia solani, an important fungal pathogen. The calcium limiting condition promotes mycophagy while high calcium environment prevents it. The expression of various T3SS apparatus encoding genes of NGJ1 was induced and secretion of several potential T3SS effector proteins (including Bg_9562) into extracellular milieu was triggered under calcium limiting condition. Using LC-MS/MS proteome analysis, we identified several calcium regulated T3SS effector proteins of NGJ1. The expression of genes encoding some of these effector proteins was upregulated during mycophagous interaction of NGJ1 with R. solani. Further, mutation of one of these genes (endo-β-1, 3- glucanase) rendered the mutant NGJ1 bacterium defective in mycophagy while complementation with full length copy of the gene restored its mycophagous activity.ConclusionOur study provides evidence that low calcium environment triggers secretion of various T3SS effectors proteins into the extracellular milieu and suggests the importance of cocktail of these proteins in promoting mycophagy.

Differentiation of human colon tissue in culture: Effects of calcium on trans-epithelial electrical resistance and tissue cohesive properties.

Background and aimsHuman colonoid cultures maintained under low-calcium (0.25 mM) conditions undergo differentiation spontaneously and, concomitantly, express a high level of tight junction proteins, but not desmosomal proteins. When calcium is included to a final concentration of 1.5–3.0 mM (provided either as a single agent or as a combination of calcium and additional minerals), there is little change in tight junction protein expression but a strong up-regulation of desmosomal proteins and an increase in desmosome formation. The aim of this study was to assess the functional consequences of calcium-mediated differences in barrier protein expression.MethodsHuman colonoid-derived epithelial cells were interrogated in transwell culture under low- or high-calcium conditions for monolayer integrity and ion permeability by measuring trans-epithelial electrical resistance (TEER) across the confluent monolayer. Colonoid cohesiveness was assessed in parallel.ResultsTEER values were high in the low-calcium environment but increased in response to calcium. In addition, colonoid cohesiveness increased substantially with calcium supplementation. In both assays, the response to multi-mineral intervention was greater than the response to calcium alone. Consistent with these findings, several components of tight junctions were expressed at 0.25 mM calcium but these did not increase substantially with supplementation. Cadherin-17 and desmoglein-2, in contrast, were weakly-expressed under low calcium conditions but increased with intervention.ConclusionsThese findings indicate that low ambient calcium levels are sufficient to support the formation of a permeability barrier in the colonic epithelium. Higher calcium levels promote tissue cohesion and enhance barrier function. These findings may help explain how an adequate calcium intake contributes to colonic health by improving barrier function, even though there is little change in colonic histological features over a wide range of calcium intake levels.

Insight on the nanoscale chemical degradation mechanism of MgCl2 attack in cement paste

The MgCl2 induced material degradation is the major durability issue facing the cement-based system. In this study, the degradation mechanism induced by MgCl2 attack at nanoscale is investigated for cement paste exposed to MgCl2 solution with different concentrations for 28 and 180 days by combing X-ray diffraction (XRD), 29Si and 27Al Nuclear Magnetic Resonance Spectroscopy (NMR), Scanning electron microscope-energy dispersive spectrometer (SEM-EDS) and thermodynamic modeling. The XRD, SEM-EDS and NMR results show that the cement paste exposed to 5 ~ 15 wt% MgCl2 cause disintegration of the main hydration product, calcium aluminosilicate hydrate (C–A–S–H) gel, portlandite, along with the formation of extensive Friedel’s salt, brucite precipitation and the small amount of ettringite. The phase transformation is closely related with the polymerization of the C–A–S–H gel and the de-aluminization characterized by the increasing mean silicate chain length and reduction of the Al[4]/Si ratio in the low calcium environment induced by MgCl2 attacking. Additionally, the predicted phase diagram from thermodynamic modeling matches well with the experimental analysis and gives a supplement support to the phase transformation. By correlating the phase composition change and the local structure of aluminate species and polymerization evolution, this study provides molecular insight on the fundamental MgCl2 induced degradation reactions happening in cement paste.

The influence of Ca2+ concentration on voltage-dependent L-type calcium channels' expression in the marbled eel (Anguilla marmorata)

The catadromous species, eels, invariably exposed to variable Ca2+ concentrations circumstance i.e., lagoon or ocean. They need to maintain Ca2+ homeostasis by exchanging Ca2+ under different culture conditions. To understand the effects of environmental Ca2+ to fish, three types of genes coding for voltage-dependent L-type calcium channels (cacnb1, 2, 3) were cloned by screening an A. marmorata cDNA library. Tissue distribution analysis of Western blot showed that Cacnb1, 2, 3 had a significantly high expression in gill; while mRNA results showed the expressions of cacnb1 and cacnb3 were predominated in skin tissue but only cacnb2 was expressed in intestine. Serum osmolality and Ca2+ concentrations of A.marmorata were increased in a high calcium environment while reduced in a low calcium environment within 7 days; however, they were not significantly different among Ca2+ treatments after the eels were acclimated for 7 days. We also examined the influence of ambient Ca2+ levels on cacnbs expression of eels. With the increasing of exposure time, mRNA and protein expressions of cacnb1 were up-regulated in high level of Ca2+ (10 mM) and down-regulated in deficient Ca2+ (0 mM) compared to the control Ca2+ (2 mM). However, the opposite results were observed in cacnb2 and cacnb3. Notably, the cacnb2 expression was not significant different among Ca2+ treatments on day 7. Our study provided the insightful evidence that cacnbs play important roles in maintaining Ca2+ homeostasis of fish.

2031 - Maintenance of Hematopoietic Stem Cells in a Low Calcium Environment

2031 - Maintenance of Hematopoietic Stem Cells in a Low Calcium Environment

Calcium-dependent disorder-to-order transitions are central to the secretion and folding of the CyaA toxin of Bordetella pertussis, the causative agent of whooping cough

The adenylate cyclase toxin (CyaA) plays an essential role in the early stages of respiratory tract colonization by Bordetella pertussis, the causative agent of whooping cough. Once secreted, CyaA invades eukaryotic cells, leading to cell death. The cell intoxication process involves a unique mechanism of translocation of the CyaA catalytic domain directly across the plasma membrane of the target cell. Herein, we review our recent results describing how calcium is involved in several steps of this intoxication process. In conditions mimicking the low calcium environment of the crowded bacterial cytosol, we show that the C-terminal, calcium-binding Repeat-in-ToXin (RTX) domain of CyaA, RD, is an extended, intrinsically disordered polypeptide chain with a significant level of local, secondary structure elements, appropriately sized for transport through the narrow channel of the secretion system. Upon secretion, the high calcium concentration in the extracellular milieu induces the refolding of RD, which likely acts as a scaffold to favor the refolding of the upstream domains of the full-length protein. Due to the presence of hydrophobic regions, CyaA is prone to aggregate into multimeric forms in vitro, in the absence of a chaotropic agent. We have recently defined the experimental conditions required for CyaA folding, comprising both calcium binding and molecular confinement. These parameters are critical for CyaA folding into a stable, monomeric and functional form. The monomeric, calcium-loaded (holo) toxin exhibits efficient liposome permeabilization and hemolytic activities in vitro, even in a fully calcium-free environment. By contrast, the toxin requires sub-millimolar calcium concentrations in solution to translocate its catalytic domain across the plasma membrane, indicating that free calcium in solution is actively involved in the CyaA toxin translocation process. Overall, this data demonstrates the remarkable adaptation of bacterial RTX toxins to the diversity of calcium concentrations it is exposed to in the successive environments encountered in the course of the intoxication process.

Environmental calcium and variation in yolk sac size influence swimming performance in larval lake sturgeon (Acipenser fulvescens).

In many animal species, performance in the early life stages strongly affects recruitment to the adult population; however, factors that influence early life history stages are often the least understood. This is particularly relevant for lake sturgeon, Acipenser fulvescens, living in areas where environmental calcium concentrations are declining, partly due to anthropogenic activity. As calcium is important for muscle contraction and fatigue resistance, declining calcium levels could constrain swimming performance. Similarly, swimming performance could be influenced by variation in yolk sac volume, because the yolk sac is likely to affect drag forces during swimming. Testing swimming performance of larval A. fulvescens reared in four different calcium treatments spanning the range of 4-132 mg l-1 [Ca2+], this study found no treatment effects on the sprint swimming speed. A novel test of volitional swimming performance, however, revealed reduced swimming performance in the low calcium environment. Specifically, volitionally swimming larvae covered a shorter distance before swimming cessation in the low calcium environment compared with the other treatments. Moreover, sprint swimming speed in larvae with a large yolk sac was significantly slower than in larvae with a small yolk sac, regardless of body length variation. Thus, elevated maternal allocation (i.e. more yolk) was associated with reduced swimming performance. Data suggest that larvae in low calcium environments or with a large yolk sac exhibit reduced swimming performance and could be more susceptible to predation or premature downstream drift. Our study reveals how environmental factors and phenotypic variation influence locomotor performance in a larval fish.

Sea anemone proteins repair damaged mouse cochlear hair cells

Summer is always the best time of year to get a good blasting at a festival or mega-band concert, but how many of us give a thought to our delicate sense of hearing as our ears are assaulted? Birds are capable of replacing damaged hair cells in the inner ear after exposure to loud sound, but mammals are not, potentially leading to deafness. However, Glen Watson from the University of Louisiana at Lafayette, USA, explains that one remarkably resilient animal has no problem rescuing damaged hair cells. Sea anemones, which detect passing prey with the vibration-sensitive hair cells covering their tentacles, have remarkable regenerative properties that allow them to rebuild the missing halves of their bodies when they tear themselves in two during reproduction. ‘It occurred to me that if any animal could recover from damage to its hair bundles, anemones would be the ones’, says Watson. Having discovered a cocktail of proteins in the mucus coating sea anemone bodies that allows them to repair injured hair cells in as little as 8 min, Watson and Pei-Ciao Tang decided to find out what effect the restorative proteins might have on damaged mouse cochlear cells.Recalling that growing the delicate hair cells derived from mouse cochlear cells in the lab was very challenging, Watson explains how he and Tang eventually succeeded in dissecting the minute cochleae and attaching the cultured cells to coverslips thanks to advice from Karen Smith and other colleagues. Watson also describes how hair cells have a bundle of minute hair-like structures on the surface – stereocilia – that are tethered at the tips by protein strands in a V-shaped formation and he explains that it is the tethers that break when hair cells are damaged, causing the stereocilia to collapse. Knowing that calcium is an essential component of the tether structures, Watson and Tang transferred the hair cells to an environment lacking calcium for 15 min in an attempt to reproduce the destruction produced by sound in mammalian cochleae. Describing the effects, Watson says, ‘The stereocilia splayed rather than occurring in well-organised bundles’. In addition, the hair cells were unable to take up a dye that undamaged hair cells absorb readily; they were severely damaged, in much the same way that the cells in our cochleae are damaged by loud sound.Having confirmed that the low calcium environment was destructive, Watson and Tang collected the mucus from starlet sea anemones that had damaged tentacle hair cells, isolated the repair proteins and added the protein cocktail to the damaged mouse hair cells for 1 h.The hair cells recovered significantly – the stereocilia were no longer splayed and the cells improved sufficiently to absorb the dye; the sea anemone proteins had repaired the damaged mouse cells. Watson and Tang then searched the mouse genome for examples of the crucial repair proteins and found evidence that mice produce many proteins that are closely related to the sea anemone repair proteins, suggesting that it may be possible to mobilise the same repair mechanisms in mammals with damaged hearing. Watson hopes that this ground-breaking discovery will eventually lead to a treatment for patients with hearing loss. However, he acknowledges that this research is in its infancy and is keen to discover the mechanism that could eventually allow sea anemones to restore our hearing.

Temporal changes in cladoceran assemblages subjected to a low calcium environment: combining the sediment record with long-term monitoring data

Lakewater calcium (Ca) decline affects softwater lakes across the Canadian Shield. Ca decline is one consequence of acid deposition, and has impeded biological recovery in formerly acidified lakes. Reduced Ca availability may advantage taxa better adapted to low Ca waters. Crosson Lake in south-central Ontario (Canada) has an extensive monitoring record and has experienced strong Ca decline since the late 1970s, recently falling below 1.5 mg L−1, a threshold value for some large Daphnia O.F. Muller, 1785 taxa. Paleolimnological analysis of the sedimentary cladoceran assemblages revealed that changes associated with the Ca decline began in the early 1970s. Relative abundances of the jelly-clad Holopedium glacialis Rowe, 2007 and the Daphnia pulex complex increased while Ca-sensitive members of the Daphnia longispina complex decreased. Zooplankton net hauls (1981–2010) corroborate the paleolimnological analysis, revealing that increases in the D. pulex complex were due to Daphnia catawba Coker, 1926 (a taxon tolerant of low Ca). Lakewater Ca, dissolved organic carbon and total phosphorus explain a significant amount of variation within the cladoceran community; however, the relationship between Ca concentration and the daphniid community was most apparent. The Crosson Lake paleolimnological and direct monitoring data may describe ecological changes that are also occurring in many other softwater lakes across the Canadian Shield and elsewhere.

Structural Models of an Intrinsically Disordered Protein Adapted for Bacterial Secretion

Many Gram-negative bacteria use Type I secretion systems, T1SS, to secrete virulence factors that contain calcium-binding Repeat-in-ToXin (RTX) motifs. Here, we present structural models of an RTX protein, RD, in both its intrinsically disordered calcium-free Apo-state and its folded calcium-bound Holo-state. Apo-RD behaves as a disordered polymer chain comprising several statistical elements that exhibit local rigidity with residual secondary structure. Holo-RD is a folded multi-domain protein with an anisometric shape. RTX motifs thus appear remarkably adapted to the structural and mechanistic constraints of the secretion process. In the low calcium environment of the bacterial cytosol, Apo-RD is an elongated disordered coil appropriately sized for transport through the narrow secretion machinery. The progressive folding of Holo-RD in the extracellular calcium-rich environment as it emerges form the TISS may then favor its unidirectional export through the secretory channel. This process is relevant for hundreds of bacterial species producing virulent RTX proteins.

Structural models of intrinsically disordered and calcium-bound folded states of a protein adapted for secretion.

Many Gram-negative bacteria use Type I secretion systems, T1SS, to secrete virulence factors that contain calcium-binding Repeat-in-ToXin (RTX) motifs. Here, we present structural models of an RTX protein, RD, in both its intrinsically disordered calcium-free Apo-state and its folded calcium-bound Holo-state. Apo-RD behaves as a disordered polymer chain comprising several statistical elements that exhibit local rigidity with residual secondary structure. Holo-RD is a folded multi-domain protein with an anisometric shape. RTX motifs thus appear remarkably adapted to the structural and mechanistic constraints of the secretion process. In the low calcium environment of the bacterial cytosol, Apo-RD is an elongated disordered coil appropriately sized for transport through the narrow secretion machinery. The progressive folding of Holo-RD in the extracellular calcium-rich environment as it emerges form the T1SS may then favor its unidirectional export through the secretory channel. This process is relevant for hundreds of bacterial species producing virulent RTX proteins.

Self Tuning of Hair Cell Bundle after Prolonged Deflection

Active hair bundle motility is one of the signatures of the amplification mechanism in non-mammalian hair cells. Here we impose high-amplitude deflections on the hair bundle for 0.1-50 seconds. Due to incompleteness of the adaptation mechanism, this is expected to change the opening probability of the transduction channels, thus mechanically bringing the bundle out of its equilibrium state. Recovery of hair bundle motion was characterized, and the effects of calcium on the feedback mechanism were investigated. Traces of hair bundle motility recorded immediately post stimulation show a slow drift towards the equilibrium position, without oscillatory motion. Bundles recover their innate oscillation between 0.1 - 1 second after cessation of the stimuli, and the quiescent time (Tq) shows a strong dependence on stimulus duration. Relaxation of hair bundles is fitted by the sum of two exponentials. The shorter of the time constants is found to be in the range ∼20-50 ms, consistent with myosin-motor dynamics. The longer time constant is significantly slower, ∼0.5-1 s. Decreased calcium concentration leads to a slower spontaneous oscillation, consistent with prior results in the field. The quiescent interval induced by deflection of hair bundles in a low-calcium environment is shorter, recovering more rapidly post stimulus cessation. Blockage of the extrusion pumps that regulate its concentration inside the stereocilia was likewise seen to prolong the induced quiescence, indicating that calcium accumulation may underlie the suppression of spontaneous motility.

Changes in water chemistry can disable plankton prey defenses

The effectiveness of antipredator defenses is greatly influenced by the environment in which an organism lives. In aquatic ecosystems, the chemical composition of the water itself may play an important role in the outcome of predator-prey interactions by altering the ability of prey to detect predators or to implement defensive responses once the predator's presence is perceived. Here, we demonstrate that low calcium concentrations (<1.5 mg/L) that are found in many softwater lakes and ponds disable the ability of the water flea, Daphnia pulex to respond effectively to its predator, larvae of the phantom midge, Chaoborus americanus. This low-calcium environment prevents development of the prey's normal array of induced defenses, which include an increase in body size, formation of neck spines, and strengthening of the carapace. We estimate that this inability to access these otherwise effective defenses results in a 50-186% increase in the vulnerability of the smaller juvenile instars of Daphnia, the stages most susceptible to Chaoborus predation. Such a change likely contributes to the observed lack of success of daphniids in most low-calcium freshwater environments, and will speed the loss of these important zooplankton in lakes where calcium levels are in decline.

How Stress Alters Memory in ‘Smart’ Snails

Cognitive ability varies within species, but whether this variation alters the manner in which memory formation is affected by environmental stress is unclear. The great pond snail, Lymnaea stagnalis, is commonly used as model species in studies of learning and memory. The majority of those studies used a single laboratory strain (i.e. the Dutch strain) originating from a wild population in the Netherlands. However, our recent work has identified natural populations that demonstrate significantly enhanced long-term memory (LTM) formation relative to the Dutch strain following operant conditioning of aerial respiratory behaviour. Here we assess how two populations with enhanced memory formation (i.e. ‘smart’ snails), one from Canada (Trans Canada 1: TC1) and one from the U.K. (Chilton Moor: CM) respond to ecologically relevant stressors. In control conditions the Dutch strain forms memory lasting 1–3 h following a single 0.5 h training session in our standard calcium pond water (80 mg/l [Ca2+]), whereas the TC1 and CM populations formed LTM lasting 5+ days following this training regime. Exposure to low environmental calcium pond water (20 mg/l [Ca2+]), which blocks LTM in the Dutch strain, reduced LTM retention to 24 h in the TC1 and CM populations. Crowding (20 snails in 100 ml) immediately prior to training blocks LTM in the Dutch strain, and also did so in TC1 and CM populations. Therefore, snails with enhanced cognitive ability respond to these ecologically relevant stressors in a similar manner to the Dutch strain, but are more robust at forming LTM in a low calcium environment. Despite the two populations (CM and TC1) originating from different continents, LTM formation was indistinguishable in both control and stressed conditions. This indicates that the underlying mechanisms controlling cognitive differences among populations may be highly conserved in L. stagnalis.

Calcium-induced Folding of Intrinsically Disordered Repeat-in-Toxin (RTX) Motifs via Changes of Protein Charges and Oligomerization States

Ligand-induced disorder-to-order transition plays a key role in the biological functions of many proteins that contain intrinsically disordered regions. This trait is exhibited by so-called RTX (repeat-in-toxin) motifs found in many virulence factors secreted by numerous gram-negative pathogenic bacteria: RTX proteins are natively disordered in the absence of calcium but fold upon calcium binding. The adenylate cyclase toxin (CyaA) produced by Bordetella pertussis, the causative agent of whooping cough, contains ∼40 RTX motifs organized in five successive blocks separated by non-RTX flanking regions. This RTX domain mediates toxin binding to its eukaryotic cell receptor. We previously showed that the last block of the RTX domain, block V, which is critical for CyaA toxicity, exhibits the hallmarks of intrinsically disordered proteins in the absence of calcium. Moreover, the C-terminal flanking region of CyaA block V is required for its calcium-induced folding. Here, we describe a comprehensive analysis of the hydrodynamic and electrophoretic properties of several block V RTX polypeptides that differ in the presence and/or length of the flanking regions. Our results indicate that the length of the C-terminal flanking region not only controls the calcium-induced folding but also the calcium-induced multimerization of the RTX polypeptides. Moreover, we showed that calcium binding is accompanied by a strong reduction of the net charge of the RTX polypeptides. These data indicate that the disorder-to-order transition in RTX proteins is controlled by a calcium-induced change of the polypeptide charges and stabilized by multimerization.

The influence of environmental calcium concentrations on calcium flux, compensatory drinking and epithelial calcium channel expression in a freshwater cartilaginous fish

Calcium metabolism and mRNA levels of the epithelial calcium channel (ECaC) were examined in a freshwater cartilaginous fish, the lake sturgeon Acipenser fulvescens. Lake sturgeon were acclimated for ≥2 weeks to 0.1 (low), 0.4 (normal) or 3.3 (high) mmol l(-1) environmental calcium. Whole-body calcium flux was examined using (45)Ca as a radioactive marker. Net calcium flux was inward in all treatment groups; however, calcium influx was greatest in the low calcium environment and lowest in the high calcium environment, whereas efflux had the opposite relationship. A significant difference in the concentration of (45)Ca in the gastrointestinal tract (GIT) of fish in the low calcium environment led to the examination of drinking rate and calcium flux across the anterior-middle (mid) intestine. Drinking rate was not different between treatments; however, calcium influx across the mid-intestine in the low calcium treatment was significantly greater than that in both the normal and high calcium treatments. The lake sturgeon ECaC was 2831 bp in length, with a predicted protein sequence of 683 amino acids that shared a 66% identity with the closest sequenced ECaCs from the vertebrate phyla. ECaC mRNA levels were examined in the gills, kidney, pyloric caeca, mid-intestine and spiral intestine. Expression levels were highest in the gills, then the kidneys, and were orders of magnitude lower in the GIT. Contrary to existing models for calcium uptake in the teleost gill, ECaC expression was greatest in high calcium conditions and kidney ECaC expression was lowest in low calcium conditions, suggesting that cellular transport mechanisms for calcium may be distinctly different in these freshwater cartilaginous fishes.

The relation between c-fos mRNA expression and protein kinase C activity in the MC3T3-E1 cells under a low calcium environment as a periodontal disease model

The relation between c-fos mRNA expression and protein kinase C activity in the MC3T3-E1 cells under a low calcium environment as a periodontal disease model

Studies on tooth germs in organ culture (Part 1) Alkaline and acid phosphatase activities in the first lower molar tooth germs cultivated under the low-calcium environment

Studies on tooth germs in organ culture (Part 1) Alkaline and acid phosphatase activities in the first lower molar tooth germs cultivated under the low-calcium environment

Effect of acute exposure to low environmental calcium on respiration and locomotion in Lymnaea stagnalis (L.)

Environmental calcium is a major factor affecting the distribution of freshwater gastropods. Whilst the effects on growth and morphology are fairly well understood, little is known about how calcium availability affects other aspects of gastropod biology. Lymnaea stagnalis (L.) is considered a calciphile and exhibits reduced growth and survival in environments containing less than 20 mg l(-1) Ca(2+). Many freshwater systems exhibit fluctuations in calcium concentration over time: where calcium levels are normally high there may be periods of low [Ca(2+)], for example following periods of flooding. Here we examined the effects of acute periods of low (20 mg l(-1)) environmental calcium on the physiology and behaviour of L. stagnalis, specifically measuring how locomotion and respiration differ between high calcium (80 mg l(-1)) and low calcium (20 mg l(-1)) environments. We found that in a low calcium environment crawling speed is reduced, and that this coincides with an increase in cutaneous respiration, indicating that the increased metabolic demands of calcium acquisition at low [Ca(2+)] reduce the energy available for locomotion. Conversely we found a decrease in aerial respiration in hypoxic conditions in the low calcium relative to the high calcium environment. In conclusion, we found that acute exposure to low environmental calcium has a highly significant effect on locomotion and respiration, which may have consequences for snail fitness when no morphological effects are apparent.

Effects of parathyroidectomy in pregnant rats on the luteinizing hormone and follicle-stimulating hormone response to synthetic luteinizing hormone-releasing hormone in the infantile offspring.

Effects of parathyroidectomy (PTx) in the rat at the 5th day of gestation on the functional development of gonadotrophin secretion in the infantile offspring was examined. A single subcutaneous injection of 10 micrograms/kg of luteinizing hormone-releasing hormone (LHRH) induced a significant increase in serum follicle stimulating hormone (FSH) and luteinizing hormone (LH) in control- and PTx-F1 male and female rats already at 3 days of age. The response in female rats was greater than in males at all ages examined. In the control- and PTx-F1 rats, age-related increase in the responsiveness to LHRH was observed in both sexes for LH but only in females for FSH. However, LH and FSH release by LHRH in the PTx-F1 female rats was significantly lower than that in control females at 14 and 22 days of age. In the PTx-F1 male rats, only FSH response to LHRH showed a tendency to decrease at 22 days of age. Serum calcium levels in 3-day-old PTx-F1 male and female rats were significantly lower than those in controls but only a slight decrease was observed in the PTx-F1 rats at other ages. The present results indicated that a low serum calcium environment during fetal life in the rat affects the functional development of pituitary responsiveness to LHRH, particularly in females.