Assessment of molasses-urea blocks for goat and sheep production in the Sultanate of Oman: intake and growth studies.

The goal of this study was to develop a molasses-urea block (MUB) for purposes of supplementing trace minerals to domestic ruminant livestock in Oman. To accomplish this, the utility of molasses and date syrup as fermentable energy sources, of straw, date flakes and wheat bran as fibre sources, and of cement and lime as binders were evaluated. The proportion of cement needed for adequate hardening of the block was also studied. Molasses- and date syrup-based blocks hardened equally well. However, the higher cost of date syrup precluded its use. Wheat straw yielded a low-density block that hardened slowly. Date fibre retained moisture and hardened extremely slowly. Wheat bran-based blocks hardened quickly and yielded dense blocks. Hence, wheat bran was judged to be the superior source of fibre. Lime did not effectively bind the blocks. A cement content of 15% allowed hardening of the blocks within 2-3 weeks. A level of 10% cement in the block reduced the hardening rate by about 50%. Sheep and goats consumed both the straw- and wheat bran-based blocks but at different rates. Consumption of the straw-based block by sheep ranged from 50 to 179 g/head per day, whereas the denser wheat bran-based block was consumed at a rate of 8-20 g/head per day. Consumption of the straw-based block by goats was low (8 g/head per day) compared to that of wheat bran-based blocks (16-24 g/head per day). On the basis of the intake of the bran-based block by sheep, a block was designed that would provide approximately 50% of an animal's trace mineral requirements per day. This block consisted of 45% molasses, 10% urea, 5% trace minerals, 2.5% NaCl, 22.5% wheat bran and 15% cement. Sheep consuming this block gained more weight than sheep fed a conventional mineral block or sheep receiving no mineral supplementation. MUBs are inexpensive (9.5 US cents/kg). We conclude that MUBs have utility for providing trace elements in ruminant diets.

Nutritional evaluation of solar dried sardines as a ruminant protein supplement.

Solar dried sardines of various qualities were analyzed for nutrient content and for nutrient digestibility and nitrogen balance in sheep. Additionally, key serum enzymes and metabolites were examined to identify potential toxic effects. Dried sardine protein, ether extract and crude ash content ranged from 65 to 39%, 5.7 to 5.1%, and 22 to 51%, respectively, for high to low quality dried sardines. Visual appraisal of the dried sardines did not appear to be very reliable for determining dried sardine quality. Crude protein content was highly correlated (r(2)=0.962) with crude ash content based on the following equation (dry matter basis): crude protein%=86.0 - (0.961xcrude ash%). Therefore, crude ash could be used to estimate crude protein content and dried sardine quality. Digestibility in Omani sheep was determined on diets composed of a composite of dried sardines collected from Al-Batinah region of the Sultanate (the average crude protein content was 51%) and compared to that of a similar diet using soybean meal (also 51% crude protein) as the major protein source. The digestibility of crude protein, ether extract, total carbohydrates, digestible energy and metabolizable energy in diets utilizing dried sardines versus the soybean meal diet were 74 versus 76%, 69 versus 68%, 67 versus 69%, 64 versus 66%, and 52 versus 56%, respectively. Although, protein digestibility was similar, nitrogen balance data suggested that nitrogen in the dried sardine diet was not as efficiently utilized as nitrogen in the soybean meal diet. Key serum enzymes and metabolites did not suggest that dried sardines at 10% of the total dietary intake would cause metabolic disturbances in sheep. The study suggests that solar dried sardines may be effectively used in ruminant diets but may not have the protein by-pass value of commercial, processed fish meals.

Calcitonin gene- and parathyroid hormone-related peptides in preeclampsia: effects of magnesium sulfate.

OBJECTIVE: To determine whether circulating levels of calcitonin gene-related peptide (CGRP) and parathyroid hormone-related peptide (PTHrP) are altered in preeclampsia, and to assess the effects of magnesium sulfate therapy on circulating levels of these two peptides. METHODS: The study population included 25 women with preeclampsia and 25 normotensive controls of similar gestational age. The effects of magnesium sulfate therapy were evaluated in 17 of the 25 preeclamptic women. Circulating levels of immunoreactive CGRP and PTHrP, including calcium, magnesium, and phosphate in the maternal and umbilical cord serum were measured. RESULTS: The frequency of preeclampsia subjects with nondetectable PTHrP (under 3 pg/mL) was significantly higher (92% versus 48%, P <.001), whereas maternal serum CGRP levels were significantly lower (50 +/- 19 versus 90 +/- 23 pg/mL, P <.001). Similarly, the frequency of newborns with nondetectable PTHrP levels in umbilical serum was significantly higher (68% versus 36%, P <.05), whereas the levels of CGRP were significantly lower (67 +/- 17 versus 79 +/- 16 pg/mL, P <.05). Magnesium sulfate treatment resulted in a significant increase in maternal circulating CGRP levels (64 +/- 17 versus 47 +/- 18 pg/mL, P <.05) with no changes in PTHrP. CONCLUSION: Maternal circulating PTHrP and CGRP concentrations were significantly lower in women with preeclampsia, which may contribute to the development and maintenance of hypertension during pregnancy. Furthermore, magnesium sulfate therapy increased the levels of CGRP in the maternal circulation.

Negative balance of calcium during lactation in marginally nourished women.

Thirty-three rural Mexican women (age, 18-36y; weight, 50.3+/-3 kg; height, 148.3+/-2 cm) were studied under metabolic balance conditions. The objectives were to study the metabolic balances of calcium and phosphorus at the 1st, 3rd, and 6th months of lactation and postweaning and to determine the incorporation of calcium and phosphorus in milk. Subjects were divided into 5 groups of 5 to 10 each, representing: the 1st, 3rd, and 6th month of lactation, postweaning, and a control group of nonpregnant, nonlactating women. Metabolic balance was determined using identical diets and analysis of 24-hour urine (3 d), 72-hour feces, and 24-hour milk samples. Calcium content was determined by atomic absorption spectrophotometry and phosphorus by a colorimetric method. Calcium content in milk was similar at the 1st, 3rd, and 6th months. Positive calcium balances were observed in the control group, while balances were very negative in all lactation groups (-721.6+/-248 mg/d). Calcium urinary excretion was higher in the control and postweaning groups (P < 0.05), suggesting a regulatory mechanism to conserve calcium during lactation. No differences were observed in phosphorus content in milk at the 1st, 3rd, and 6th months. Positive balances were observed in the control and postweaning groups (331+/-139 and 87.1+/-130 mg/d, respectively, mean +/- SD), while the lactation groups presented more subjects (approximately 75%) in negative balance (mean +/- SD of -180.6+/-392 to -439+/-146 mg/d). High fecal calcium and phosphorus excretion (approximately 1,500 mg/d) likely contributed to the negative balance during lactation.

Identification of a 25-hydroxyvitamin D3 1alpha-hydroxylase gene transcription product in cultures of human syncytiotrophoblast cells.

Although accumulating data show that placenta is able to synthesize 1,25-dihydroxyvitamin D3, the presence of cytochrome P(450) enzyme capable of converting 25-hydroxyvitamin D3 (250HD(3)) to the biologically active form of vitamin D in this tissue, has not been yet clearly established. In this study, we have investigated the presence of 25-hydroxyvitamin D3 1alpha-hydroxylase (1alpha-(OH)ase) gene expression products in cultured human syncytiotrophoblast. Total RNA was isolated from cultured placental cells and subjected to Northern blots or RT-PCR by using 1alpha-(OH)ase-specific primers. The amplified complementary DNA fragments were analyzed by gel electrophoresis and nucleotide sequencing. Total RNA from kidney HEK 293 cells was subjected to reverse transcriptase reaction, and a 298-bp complementary DNA 1alpha-(OH)ase probe was generated by PCR. Primary cultures of human syncytiotrophoblasts exhibited 1alpha-(OH)ase activity, and a transcript for this gene could be demonstrated in these cells. Northern blot analysis revealed the presence of a 2.5-kb product, similar in size to that previously reported in kidney. RT-PCR analysis demonstrated the presence of a single transcript with nucleotide sequence identical to that previously reported for human 1alpha-(OH)ase complementary DNA clones. In addition, data are presented which suggest that differentiation of cytotrophoblast to the syncytial state was not necessary for this gene to be expressed, which may indicate a role of this enzyme all through pregnancy. The overall results of this study provide evidence for the presence of 1alpha-(OH)ase in the human placenta, suggesting that conversion of 25OHD(3) to 1,25-dihydroxyvitamin D3 in the trophoblast is most probably attributed to an enzymatic 1alpha-hydroxylation reaction.

Preeclampsia is associated with low circulating levels of insulin-like growth factor I and 1,25-dihydroxyvitamin D in maternal and umbilical cord compartments.

Insulin-like growth factor I (IGF-I) stimulates renal and placental 1,25-dihydroxyvitamin D [1,25-(OH)2D] and is considered an important regulator of fetal growth. As 1,25-(OH)2D and birth weight are low in preeclampsia, this study was undertaken to determine whether circulating levels of IGF-I were associated with serum 1,25-(OH)2D concentrations in preeclamptic (PE group) and normotensive (NT group) pregnancies. Maternal and umbilical cord serum levels of IGF-I and 1,25-(OH)2D were significantly (P < 0.01) lower in the PE group than in the NT group. The concentrations of these two hormones correlated significantly in the umbilical cord (P < 0.05) and in the maternal (P < 0.001) compartments of the PE and NT groups, respectively. The amount of IGFBP-3 was 64% lower whereas that of IGFBP-1 was 2.9-fold higher in umbilical cord serum of the PE group compared with the NT group. In addition, maternal and umbilical cord serum IGF-I correlated significantly (P < 0.05) with weight and length at birth only in the PE group. In conclusion, the results of this study indicate that circulating IGF-I and 1,25-(OH)2D levels in both maternal and umbilical cord compartments are low in preeclampsia. Furthermore, this study suggests a differential regulatory effect of IGF-I on 1,25-(OH)2D synthesis and fetal growth depending on the presence or absence of preeclampsia.

[Calcium metabolism in lactating women]. / Metabolismo de calcio en la mujer durante la lactancia.

During lactation the main source of the breast-milk calcium seems to be maternal bone. The women who breast-fed, lost bone mineral content, which is recovered once breast-feeding ceased. Breast-milk calcium do not depend on an increase in calcium intake by the lactating mother. Calcium demand during lactation is associated with adjustments in the calcium metabolism, such as a decrease in urinary calcium excretion and mobilization of calcium from maternal bone. The classical calciotropic hormones concentrations (PTH and 1,25-dihydroxyvitamin D) are not associated with bone turnover markers or with changes in bone mineral content in the lactating women. However, serum estradiol is strongly associated with calcium balance, bone loss and calcium milk content.

Effects of IGF-I on 1,25-dihydroxyvitamin D(3) synthesis by human placenta in culture.

The aim of the present study was to assess the effects of insulin-like growth factor I (IGF-I) upon the synthesis of 1, 25-dihydroxyvitamin D(3) [1,25-(OH)(2)D(3)] by human placenta trophoblasts in culture. Cytotrophoblastic cells obtained from normal term human placentae were cultured in Dulbecco's modified Eagle's medium with HEPES and glucose (DMEM-HG) during 72 h and further incubated in serum-free DMEM-F12 in the presence of IGF-I prior to the addition of [(3)H]-25-(OH)D(3) used as a precursor. The results showed that 2 h preincubation time with IGF-I was required for maximal production of [(3)H]-1,25-(OH)(2)D(3). Cultures in the presence of increasing concentrations of IGF-I (0-6.5 nmol/l), added 2 h before incubation with the labelled substrate, resulted in a dose-dependent response increment of [(3)H]-1,25-(OH)(2)D(3) production with a maximal conversion rate at the dose of 2.6 nmol/l. Higher doses of IGF-I did not result in further stimulatory effects. Co-incubations in the presence of cycloheximide significantly (P < 0. 0001) inhibited the IGF-I-mediated effects upon [(3)H]-1, 25-(OH)(2)D(3) production. Identity of putative [(3)H]-1, 25-(OH)(2)D(3) produced by human placenta was confirmed by spectral and receptor binding analysis. These results demonstrate the ability of cultured human syncytiotrophoblast cells to convert 25-(OH)D(3) to 1,25-(OH)(2)D(3) and suggest a local protein-dependent regulatory effect of IGF-I upon this biotransformation.

Effect of nutritional rehabilitation of undernourished rats on serum insulin-like growth factor (IGF)-I and IGF-binding proteins.

The aim of the present work was to study the effect of nutritional rehabilitation with different concentration of dietary protein (6, 18 or 50%) of previously undernourished rats on serum Insulin-like growth factor-I (IGF-I) and Insulin-like growth factor binding proteins levels (IGFBPs). Undernutrition was induced by feeding rats with 0.5% casein diet for 5 weeks. Over this period, growth, serum total proteins, IGF-I levels and IGFBP-3/IGFBP-2 ratio were significantly decreased compared to the group fed ad libitum 18% casein diet. Nutritional rehabilitation for 21 days with 6% casein diet did not change any of these parameters. Nutritional rehabilitation with 18 or 50% casein diet for one day did not initiate the restoration of serum IGF-I levels and IGFBP-3/IGFBP-2 ratio. However, after 10 days with 18 or 50% casein diets, there was an increase of 12 fold in IGF-I levels and 7 fold in the IGFBP-3/IGFBP-2 ratio. Finally, rehabilitation for 21 days with 18 or 50% casein diet produced an increase of 21 and 26 fold in IGF-I levels, and 6.1 and 14.5 fold in the IGFBP-3/IGFBP-2 ratio respectively. These results suggest that nutritional rehabilitation with 18% casein and above were more effective than 6% casein diets to reestablish body weight. Serum IGF-I and IGFBP-3 concentrations were sensitive indicators of the evolution of the nutritional status of the rats depending of the protein concentration in the diet in previously undernourished rats.

[Calcium and phosphorus balance in rural lactating women in Mexico]. / Balance de calcio y fósforo en mujeres lactantes rurales de México.

OBJECTIVE: To compare the balance of calcium (Ca) and phosphorus (P) between lactation and weaning, and to determine the Ca and P milk production in Mexican rural lactating women. METHODS: Thirty-six women aged 18-36 y, weight 49 +/- 3 kg and height 148 +/- 2 cm, were divided in six groups: four groups of lactation (1st, 3rd, 6th and 12th month) one post-weaning group and one of non pregnant non lactating women. The balance studies were performed collecting duplicate diets, 24 h urine for 3 days, 72 h feces and 24 h milk samples for 2 days. The Ca content was determined by atomic absorption spectrophotometry and P by the molybdate method. RESULTS AND CONCLUSIONS: Ca content in milk was higher in the 3rd month of lactation. The Ca balances were negative in all lactation groups (789 +/- 165 mg/d). Ca urinary excretion was lower in the lactating group (p < 0.05) suggesting a regulatory mechanism to conserve Ca during lactation. No differences were observed in the P content in milk and positive balances of P were observed in the non lactating and the post-weaning groups, whereas they were negative in the lactation groups (115 to 475 mg/d). High fecal Ca and P excretion (approximately 1300 mg/d) was observed, which contributed to the negative condition of the balance during lactation. The production of Ca and P in the milk of these rural women was similar to the one seen in rural and urban groups in Africa, Asia, Europe and the U.S.

Hepatic histidase gene expression responds to protein rehabilitation in undernourished growing rats.

We studied the effect of nutritional rehabilitation with a 6, 18 or 50% casein diet in undernourished rats on histidase (Hal) expression. Undernutrition was induced by feeding rats a 0.5% casein diet for 5 wk. Over this period, growth, serum total proteins and insulin-like growth factor-I (IGF-I) levels were significantly lower than those of rats that freely consumed an 18% casein diet. During this period, undernutrition also significantly reduced Hal activity and Hal-mRNA concentration. Nutritional rehabilitation for 21 d with a 6% casein diet did not change any of these variables. Nutritional rehabilitation with an 18 or 50% casein diet for 1 d initiated the restoration of Hal activity and mRNA concentration. After 10 d of consuming 18 or 50% casein diets, Hal activity was 5- and 14-fold, and mRNA concentration was 8.5- and 23-fold higher, respectively, than in the protein-undernourished group (PU). During this period, body weight, total serum proteins and IGF-I levels were also significantly (P < 0.05) higher than those of the PU group. At the end of 21 d of rehabilitation with an 18 or 50% casein diet, Hal activity was 14- and 31-fold higher and Hal mRNA concentration was 10- and 24-fold higher, respectively, than in the PU group. In conclusion, our data showed that rehabilitation of undernourished rats with a 6% casein diet was not sufficient to re-establish growth indicators, Hal activity or gene expression, and that nutritional rehabilitation with an 18 or 50% casein diet effectively re-established body weight , biochemical variables and the capacity of histidase gene expression to eliminate the excess of protein.

[Vitamin D induces proliferation in rat endometrium cultured cells]. / La vitamina D induce la proliferación de células en cultivo del endometrio de rata.

OBJECTIVE: To study the effects of 1,25-dihydroxyvitaminD3 (1,25-(OH)2D3) on proliferation and cell death in the rat uterus. MATERIAL AND METHODS: A rat endometrial cell line (Rentro 1) grown in a Dulbecco Minimal Essential Medium (DMEM) supplemented with 1% charcoal stripped serum was used in all experiments in order to eliminate the steroid hormone. Cell monolayer was incubated in the presence and absence of 1,25-(OH)2D3 or 17 beta-estradiol or vehicle. After stimulation, we evaluated cell proliferation and DNA synthesis by trypan blue counting method and flow cytofluorometry, respectively. Finally, the genomic DNA integrity was evaluated by electrophoresis and the bands visualized with ultraviolet light. RESULTS: The cells in medium containing 1% fetal bovine serum free of steroid hormones stimulated the cell growth 85% more than without serum. Supplement with albumin did not allow cell growth. The cells did not respond to 17 beta-estradiol but the presence of 1,25-(OH)2D3 induced cell proliferation. These results confirm that Rentro 1 cells do not express the estrogen receptor and demonstrate their capacity to respond to 1,25-(OH)2D3. Finally, the integrity of DNA was not affected by 1,25(OH)2D3, suggesting that this hormone is not involved in cell death by apoptosis in our cell line, as seen in other cell lines. CONCLUSIONS: 1) 1,25-dihydroxyvitamin D induced cell proliferation in the endometrial cell line Rentro 1 in a dose-dependent fashion and this effect is independent of the presence of an estrogenic stimulus; 2) the increase in cell number was related to DNA synthesis during the cell cycle; and 3) the presence of the hormone in the culture medium was not able to induce cell death.

Riboflavin and pyridoxine status in a group of pregnant Mexican women.

In order to assess the nutritional status of riboflavin and pyridoxine during pregnancy, 24 Mexican women were studied during the second trimester and 17 during the third trimester of gestation. The biochemical evaluation of the riboflavin and pyridoxine status was performed by measuring the activation coefficients (AC) of the erythrocyte glutathione reductase (eGR) and aspartate aminotransferase (eAAT), respectively. Dietary protein, riboflavin, thiamin, and calcium intake decreased significantly in the last trimester of gestation. The women presented biochemical deficiency of pyridoxine in the second and third trimester of pregnancy, but they developed biochemical deficiency of riboflavin and pyridoxine deficiency. None showed clinical signs of vitamin deficiency. No significant correlation was found between individual serum concentrations of estradiol or progesterone and eGR-AC or eAAT-AC in both trimesters of pregnancy. Six newborns studied showed normal eGR-AC and eAAT-AC.

Lower circulating insulin-like growth factor I and 1,25-dihydroxyvitamin D levels in preeclampsia.

OBJECTIVE: To assess whether the circulating levels of insulin-like growth factor I (IGF-I) are lower in preeclamptic than in normotensive pregnant women and whether serum concentrations of IGF-I are associated with those of 1,25 dihydroxyvitamin D (1,25-(OH)2D). STUDY DESIGN: The study was cross-sectional and was done at 26.7 to 39.7 weeks of pregnancy. The results obtained from preeclamptic women were compared with those obtained from normotensive pregnant women with the same gestational age (control group). SETTING: All the volunteers were patients attending the General Hospital of Mexico City and all laboratory measurements were done at the National Institute of Nutrition Salvador Zubiran, Mexico City. SUBJECTS: The study included 26 preeclamptic women and 26 normotensive pregnant women. All participated voluntarily and signed an informed consent. PROCEDURE: The following measurements were done: serum concentrations of IGF-I, 1,25-(OH)2D, intact parathyroid hormone (PTH), inorganic phosphorus, creatinine, and total and ionic calcium and magnesium. Also urinary calcium and creatinine clearance were measured and dietary and anthropometric data were obtained. All determinations were done blindly. Comparisons between groups were done using the Mann-Whitney U-test. Associations between variables were tested using the Spearman rank correlation and stepwise regression. RESULTS: Serum IGF-I levels were 26.1 +/- 10.2 nmol/L (mean +/- SD) in the preeclamptic group and 40.9 +/- 14.3 in the normotensive group (p = 0.0003); serum 1,25-(OH)2D levels were 43.6 +/- 8.2 pg/mL in the preeclamptic group and 52.1 +/- 10.2 in the normotensive group (p = 0.005). Serum intact PTH was similar in both groups. Serum levels of IGF-I, 1,25-(OH)2D, and intact PTH correlated significantly in the control group. In the preeclamptic group correlation was found only between IGF-I and 1,25-(OH)2D. CONCLUSIONS: Our study brings out two interesting observations. First, that serum IGF-I levels were significantly lower in preeclamptic than in control pregnant women; and second, the existence of a significant correlation between serum IGF-I and 1,25-(OH)2D concentrations in both preeclamptic and normotensive pregnant women.

[Synthesis of dihydroxycholecalciferols in maternal and fetal rat organs in the last days of gestation]. / Síntesis de dihidroxicolecalciferoles en órganos maternos y fetales de rata en los últimos días de la gestación.

The in vitro synthesis of 3H1,25(OH)2D3 and 3H24,25-(OH)2D3 in different maternal (kidney and spleen), placental (maternal and fetal sides) and fetal (kidney, intestine, liver and skeleton) tissues and the relative contribution of each of these organs to total production was studied in the last six days of gestation in rats. On day 16, synthesis of both metabolites was higher in fetal tissues than in maternal kidney, and decreased as gestation advanced. On day 16, placental contribution represented more than 50% of the total production of 3H1,25(OH)2D3, while the maternal kidneys and the fetal tissues contributed only 16% and 26%, respectively. On day 18, the synthesis of 3H1,25(OH)2D3 by maternal placenta and fetal tissues was significantly reduced in comparison with that observed on day 16. Between days 16 and 19, the plasma concentrations of 1,25(OH)2D in mothers and fetuses were associated with the magnitude of its in vitro production. Starting on day 19, however, the in vitro production remained at the same level while the plasma concentration increased, suggesting lower utilization or lower catabolism of this metabolite. Similarly, the total synthesis of 3H24,25(OH)2D3 decreased on day 19. Between days 16 and 18, a higher synthesis of 3H24,25(OH)2D3 corresponded with lower plasma concentration of this metabolite suggesting greater utilization. In contrast, between days 19 and 21, the in vitro synthesis and plasma concentration of 24,25(OH)2D increased in parallel fashion. In summary we report the following findings: a) inhibition of the in vitro synthesis of 3H1,25(OH)2D3 and 3H24,25(OH)2D3 on day 19 of gestation in the rat; b) the contribution of each of the different maternal, placental and fetal tissues to the total synthesis of these metabolites in the last six days of gestation; and c) a parallelism between in vitro production and plasma concentration of both metabolites.

1,25-Dihydroxyvitamin D3 induces in vivo the decidualization of rat endometrial cells.

Intraluminal injection of female rats at Day 5 of pseudopregnancy with 10-500 ng 1,25-dihydroxyvitamin D3 (1,25-(OH)2D3) significantly increased the uterine weight and induced decidual reaction. This effect was observed as early as the 3rd day after 1,25-(OH)2D3 injection. It was detectable only in the injected left horn and not in the non-injected right horn. A 500 ng dose of 25-(OH)D3 had no such effect. The present in-vivo results suggest that 1,25-(OH)2D3 may play a physiological role in endometrial cell differentiation into decidual cells, a crucial step in the process of blastocyst implantation.

Thyroid and parathyroid-independent increase in plasma 1,25-dihydroxyvitamin D during late pregnancy in the rat.

The effect of thyroparathyroidectomy (TPTX) on the plasma concentrations of the vitamin D metabolites (25-(OH)D, 24,25-(OH)2D and 1,25-(OH)2D) has been studied in pregnant rats and their fetuses during the last quarter of gestation. Maternal and fetal vitamin D metabolites were not significantly affected by TPTX. A significant increase in plasma 1,25-(OH)2D concentrations was observed in both TPTX and control mothers and fetuses from days 19 to 21. Fetal and maternal plasma 25-(OH)D were positively correlated in both control and TPTX groups. Such a correlation was also found for 24,25-(OH)2D in the two groups. In contrast, a positive correlation between maternal and fetal plasma concentrations of 1,25-(OH)2D was found in TPTX but not in control rats. These data suggest that major alterations in calcium metabolism, such as that produced by maternal TPTX, are insufficient to affect the changes in maternal and fetal plasma 1,25-(OH)2D during late pregnancy significantly. They also suggest that parathyroid hormone, thyroxine, and/or calcitonin may control a possible placental transfer of 1,25-(OH)2D in the rat.