Nonpregnant Female Rabbits Research Articles

Study on wearable pregnancy diagnosis device for rabbits based on photoelectric sensor

Pregnancy diagnosis is essential for rabbits' reproductive management, which allows for re-insemination, and reduces the laboring interval in commercial operations. This study aimed to develop a wearable, non-invasive pregnancy identification device for rabbits. A sensing probe contained three LEDs (Light wavelength is 660 nm, 850 nm, and 930 nm respectively), two Si-based photodiodes, and a host with signal processing was developed. Room-temperature-vulcanized (RTV) silicone rubber, aluminum oxide powder, and dyes of different colors were used to make the abdominal tissue phantom of pregnant female rabbits (PRs) and non-pregnant female rabbits (NPRs) to test the sampling stability of the developed device. The results showed that the variation coefficient of the sampling data of the device was<0.013, and the stability met the use requirements. Sampling data from 419 female rabbits were used to build partial least squares discrimination analysis (PLS-DA) and support vector machine (SVM) models of different abdominal hair densities, including dense hair, sparse hair, hair removal, and hair mixing. The classification results of the two models showed that SVM had the best performance, the Ac, Re, Pre, and F-score are more than 80%, respectively. Then, the trained SVM model was then used as the identification model and downloaded to the developed device. Another 218 rabbits were used to verify the performance of the developed device, and the prediction performance was the best among the hair removal rabbits, with Ac, Re, Pre, and F-socre of 83.94%, 83.67%, 81.19%, and 82.41% respectively. The results show that the wearable device developed in this study has a good prediction performance for rabbits with abdominal hair removal, and provides a new idea for pregnancy diagnosis of rabbits.

Early pregnancy diagnosis of rabbits: A non-invasive approach using Vis-NIR spatially resolved spectroscopy

Pregnancy diagnosis is essential for rabbit's reproductive management. The early identification of non-pregnant rabbits allows for earlier re-insemination, increases the service rate, and reduces the laboring interval in commercial operations. The objective of this study was to establish the feasibility of using a Vis-NIR spatially resolved spectroscopy for diagnosing pregnancy in female rabbits. A total of 141 female rabbits, including 67 pregnant female rabbits (PRs) and 74 non-pregnant female rabbits (NPRs), were measured spectrally between 350 and 1000 nm with different source-detector distances (SDD). Different preprocessing methods were used to transform and enhance the spectral signal. A partial least squares-discriminant analysis (PLS-DA) classification model of the original and preprocessed spectra was established. The highest accuracy of the calibration set and prediction set was 91.75% and 86.05%, respectively. Competitive adaptive reweighted sampling (CARS) and successive projection algorithm (SPA) were used to select characteristic wavelengths from the variables of VIP > 1 (Variable importance in projection),and four classification models were established based on selected wavelengths, including PLS-DA, support vector machine (SVM), K-Nearest Neighbor (KNN) and Naïve Bayes. SPA-SVM was the optimal classification model, the sensitivity, specificity, and accuracy of the validation set and prediction set were 93.18%, 94.44%, 93.88%, 86.96%, 90.00%, 90.69% respectively. The results showed that Vis-NIR spatially resolved spectroscopy combined with classification models could discriminate the PRs and NPRs.

Co-relation of estrous cycle phases with uterine bacterial and fungal flora in non-pregnant female laboratory rabbits.

This study was designed to investigate the relationship between the estrous cycle phases with uterine bacterial and fungal flora in non-pregnant female rabbits. Thirty laboratory mature multiparous rabbits were used for this purpose. Samples from uterine lavage for culture of bacteria and fungi were collected at different stages of estrous cycle (based on vaginal cytology), and histopathological observations were evaluated based on the scoring system used for defining the infection of the uterus. Various types of bacteria and fungi were isolated from rabbits at all stages of estrous cycle. The widest variety of bacteria and fungi was isolated at Di-estrous stage and the lowest variety was detected at estrous stage. Klebsiella oxytoca as well as yeast have been isolated at all stages of estrous cycle. This study showed that infection with K. oxytoca and yeast had no relationship with different stages of estrous cycle but other bacteria and fungus were associated with one or more stages of the estrous cycle in rabbits.

Tissue-engineered blood vessel substitute by reconstruction of endothelium using mesenchymal stem cells induced by platelet growth factors

Cardiovascular diseases remain leaders as the major causes of mortality in Western society. Restoration of the circulation through construction of bypass surgical treatment is regarded as the gold standard treatment of peripheral vascular diseases, and grafts are necessary for this purpose. The great saphenous vein is often not available and synthetic grafts have their limitations. Therefore, new techniques to produce alternative grafts have been developed and, in this sense, tissue engineering is a promising alternative to provide biocompatible grafts. This study objective was to reconstruct the endothelium layer of decellularized vein scaffolds, using mesenchymal stem cells (MSCs) and growth factors obtained from platelets. Fifteen nonpregnant female adult rabbits were used for all experiments. Adipose tissue and vena cava were obtained and subjected to MSCs isolation and tissue decellularization, respectively. MSCs were subjected to differentiation using endothelial inductor growth factor (EIGF) obtained from human platelet lysates. Immunofluorescence, histological and immunohistochemical analyses were employed for the final characterization of the obtained blood vessel substitute. The scaffolds were successfully decellularized with sodium dodecyl sulfate. MSCs actively adhered at the scaffolds, and through stimulation with EIGF were differentiated into functional endothelial cells, secreting significantly higher quantities of von Willebrand factor (0.85 μg/mL; P < .05) than cells cultivated under the same conditions, without EIGF (0.085 μg/mL). Cells with evident morphologic characteristics of endothelium were seen at the lumen of the scaffolds. These cells also stained positive for fascin protein, which is highly expressed by differentiated endothelial cells. Taken together, the use of decellularized bioscaffold and subcutaneous MSCs seems to be a potential approach to obtain bioengineered blood vessels, in the presence of EIGF supplementation.

Biotransformation of 2,3,3,3-tetrafluoropropene (HFO-1234yf) in male, pregnant and non-pregnant female rabbits after single high dose inhalation exposure

2,3,3,3-Tetrafluoropropene (HFO-1234yf) is a novel refrigerant intended for use in mobile air conditioning. It showed a low potential for toxicity in rodents studies with most NOAELs well above 10,000ppm in guideline compliant toxicity studies. However, a developmental toxicity study in rabbits showed mortality at exposure levels of 5,500ppm and above. No lethality was observed at exposure levels of 2,500 and 4,000ppm. Nevertheless, increased subacute inflammatory heart lesions were observed in rabbits at all exposure levels. Since the lethality in pregnant animals may be due to altered biotransformation of HFO-1234yf and to evaluate the potential risk to pregnant women facing a car crash, this study compared the acute toxicity and biotransformation of HFO-1234yf in male, female and pregnant female rabbits. Animals were exposed to 50,000ppm and 100,000ppm for 1h. For metabolite identification by 19F NMR and LC/MS-MS, urine was collected for 48h after inhalation exposure. In all samples, the predominant metabolites were S-(3,3,3-trifluoro-2-hydroxypropanyl)-mercaptolactic acid and N-acetyl-S-(3,3,3-trifluoro-2-hydroxypropanyl)-L-cysteine. Since no major differences in urinary metabolite pattern were observed between the groups, only N-acetyl-S-(3,3,3-trifluoro-2-hydroxypropanyl)-L-cysteine excretion was quantified. No significant differences in recovery between non-pregnant (43.10±22.35μmol) and pregnant female (50.47±19.72μmol) rabbits were observed, male rabbits exposed to 100,000ppm for one hour excreted 86.40±38.87μmol. Lethality and clinical signs of toxicity were not observed in any group. The results suggest that the lethality of HFO-1234yf in pregnant rabbits unlikely is due to changes in biotransformation patterns or capacity in pregnant rabbits.

Inhibitory effects of methotrexate on spontaneous motility and Cajal-like type of tubal interstitial cells in rabbit oviduct

To study the adverse biomechanical effects of methotrexate (MTX) on spontaneous tubal motility and on a widely distributed Cajal-like type of tubal interstitial cells (t-ICC) in rabbits. In our previous study, MTX was confirmed to cause acute endosalpingitis, and ultrastructural and steroid receptor damage in rat's endosalpinx in a dose-dependent manner. Differences in spontaneous tubal contractions and cellular distribution of t-ICC in isthmus were evaluated in response to MTX. Medical school research laboratory. Twenty nonpregnant female New Zealand albino rabbits in estrus stage were divided equally into four groups. Rabbits received IM MTX (1, 5, 10 mg/kg body weight) and controls received physiological saline. On day 7, in vitro motility studies measuring spontaneous tubal contractions were performed, and cellular distribution of t-ICC was determined by immunohistochemistry. Methotrexate produced a concentration-dependent inhibition of spontaneous isthmus contractions (frequency in 5, 10 mg/kg groups, and amplitude in 1, 5, 10 mg/kg MTX groups). It decreased significantly compared with the control group. Meanwhile, MTX at 5, 10 mg/kg decreased the population of c-kit immunoreactive t-ICC significantly. The decreased t-ICC may contribute to the diminished tubal smooth muscle contractility caused by MTX as observed. Tubal interstitial cells might be new potential targets for a variety of dysfunctional tubal motility diseases.

Experimental model of the formation of pelvic adhesions by videolaparoscopic in female rabbits

To verify the frequency of postsurgical pelvic adhesion formation in an experimental animal model using videolaparoscopy. Experimental study in a sample of 11 non-pregnant female rabbits, aged 5 to 7 months. After general anesthesia, access to the abdominal cavity was performed by an open puncture technique, with 10mm optics, placing two other 5 mm trochars under direct visualization, in the iliac fossae. Then a fragment of peritoneum was resected, followed by electrocauterization. In 21 days, the videolaparoscopy was repeated, and adhesion formation and score was looked at, with biopsies at the surgical site. 54 % of adhesion formation was observed, and the median score of adhesions was 6 (minimum of 3 and maximum of 10), all of them found in the bladder and the anterior abdominal wall. The method used presents a high frequency of intra-abdominal adhesion formation.

BEHAVIOURAL TESTING AND HISTOLOGICAL ASSESSMENTS OF RABBIT SPINAL CORD FOLLOWING INTRATHECAL ADMINISTRATION OF ONDANSETRON

1. Intrathecal injection of ondansetron has the potential to reduce opioid-related side-effects. The aim of the present study was to determine whether this route of administration produces neuraxial injury. 2. Adult, non-pregnant female New Zealand white rabbits received a single bolus injection of a low (40 microg) or high (4.0 mg) dose of ondansetron into the intrathecal space between the 4th and 5th lumbar vertebrae. In some cases, ondansetron was coadministered with morphine (5 microg/kg). Control animals received a bolus injection of normal saline. Behavioural assessments were conducted at 1 and 24 h to determine overt changes in arousal and mobility, followed by histological evaluation of the excised spinal cord. 3. Of 45 animals investigated, 10 rabbits exhibited modest behavioural evidence of spinal injury, the incidence of which was equally distributed between the treatment groups. Haematoxylin and eosin, along with HAM56, staining of cross-sections of the cervical, thoracic and upper and lower lumbar areas revealed mild signs of inflammation. This, too, was equally distributed between the treatment groups, suggesting that any observed neuraxial injury was the result of needle trauma and not ondansetron neurotoxicity. 4. Collectively, these negative findings support conducting further experiments to fully assess the clinical usefulness of intrathecal ondansetron administration.

Reperfusion injury after detorsion of unilateral ovarian torsion in rabbits

Objective: To determine if reperfusion injury takes place in ovarian tissue following the detorsion of the torsioned ovary. Study design: Fifty-four New Zealand mature nonpregnant female rabbits were divided into six groups. One group served to determine the basal values of thiobarbituric acid reacting substance (TBARS) and another group was sham. In the third and fourth groups, ovarian torsions and subsequent oophorectomy were performed in 1 and 3 h, respectively. In the fifth and sixth groups, detorsions were carried out after unilateral ovarian torsion lasting 1 and 3 h, respectively, then oophorectomies of the detorsioned ovaries were performed 2 h after detorsion. The level of TBARS in ovarian tissues was determined in all subjects. Statistical analysis was performed using analysis of variance and Duncan’s multiple range test. Differences were considered to be significant if P<0.05. Results: The levels of TBARS were not different in the basal and sham groups ( P>0.05), while ovarian torsion caused significant increase in TBARS in the ovary ( P<0.05), and detorsion caused a further significant increase in ovarian TBARS ( P<0.05). Conclusion: Reperfusion injury in ovarian tissue, following the detorsion after the torsion of the ovary lasting up to 3 h was demonstrated biochemically in this study.

Raloxifene acutely relaxes rabbit coronary arteries in vitro by an estrogen receptor-dependent and nitric oxide-dependent mechanism.

Selective estrogen receptor modulators (SERMs) have been defined as compounds that display tissue specificity with regard to estrogenic effects. They appear to share the beneficial effects of estrogen on bone and lipids but are not associated with an increased risk of breast or uterine carcinoma. Estrogen relaxes coronary arteries and has long-term protective effects on the vascular system. The effect of SERMs on the coronary vasculature is unknown. We therefore investigated the effects of the SERM raloxifene on isolated rabbit coronary arteries. Rings of coronary artery from adult male and nonpregnant female New Zealand White rabbits were suspended in organ baths containing Krebs solution; isometric tension was then measured. Raloxifene induced coronary arterial relaxation in male and female coronary arteries by an endothelium-dependent and estrogen receptor-dependent mechanism involving nitric oxide. Raloxifene also had a direct calcium antagonistic effect on the coronary myocyte. Estrogen, however, induced only endothelium-independent coronary arterial relaxation. The endothelium-dependent component of relaxation induced by raloxifene 10(-6) mol/L resulted in almost 100% (79+/-7% versus 43+/-3%, P<0.001) more relaxation than that induced by estrogen 10(-6) mol/L. These data demonstrate that raloxifene has vascular relaxing properties. The surprising finding is that the receptor-dependent effects via the endothelium are observed in coronary arteries from both male and female animals.

Testosterone relaxes rabbit coronary arteries and aorta.

Until menopause, women appear to be protected from coronary heart disease. Evidence suggests that estrogen may play a role in the protection of the cardiovascular system by exerting a beneficial effect on risk factors such as cholesterol metabolism and by a direct effect on the coronary arteries. To date there has been no evidence linking testosterone with the occurrence of coronary heart disease. Testosterone may affect the cardiovascular system directly, thus partially explaining the difference in the incidence of coronary artery disease in men and premenopausal women. The purpose of this study was to assess the direct effect of testosterone and a number of testosterone analogues on rabbit coronary arteries and aorta in vitro. Rings of coronary artery and aorta of adult male or nonpregnant female New Zealand White rabbits were suspended in organ baths containing Krebs solution; isometric tension then was measured. The response to testosterone was investigated in prostaglandin F2 alpha (PGF 2 alpha)- and KCl-contracted rings. The effects of endothelium and nitric oxide synthase, prostaglandin synthetase, and guanylate cyclase inhibition on testosterone-induced relaxation were investigated. The effects of ATP-sensitive potassium channels and potassium conductance were also assessed. Relaxing responses in the presence of aromatase inhibition and testosterone receptor blockade were performed. The relaxing responses to the testosterone analogues etiocholan-3 beta-ol-17-one, epiandrosterone, 17 beta-hydroxy-5 alpha-androst-1-en-3-one, androst-16-en-3-ol, and testosterone enanthanate were measured. Testosterone relaxed rabbit coronary arteries and aorta. There was no significant difference between the relaxation effect of testosterone with or without endothelium. Similar results were obtained from male and nonpregnant female rabbits. The relaxing response of testosterone in the coronary artery was significantly greater than in the aorta. The relaxing response of testosterone in the coronary artery was significantly reduced by the potassium channel inhibitor barium chloride but not by the ATP-sensitive potassium channel inhibitor glibenclamide. The relaxing response to testosterone was greater in PGF 2 alpha-contracted rings compared with KCl-contracted rings. Inhibitors of nitric oxide synthase, prostaglandin synthetase, and guanylate cyclase did not affect relaxation induced by testosterone. Inhibition of aromatase and testosterone receptors did not affect relaxation. Testosterone did not shift the rabbit coronary arterial calcium concentration-dependent contraction curves, whereas verapamil did. There were, however, significant differences in the relaxing response to testosterone compared with testosterone analogues. Testosterone was the most potent relaxing agent, suggesting that there may be a structure-function relation in the relaxing response. Testosterone induces endothelium-independent relaxation in isolated rabbit coronary artery and aorta, which is neither mediated by prostaglandin I2 or cyclic GMP. Potassium conductance and potassium channels but not ATP-sensitive potassium channels may be involved partially in the mechanism of testosterone-induced relaxation. The in vitro relaxation is independent of sex and of a classic receptor. The coronary artery is significantly more sensitive to relaxation by testosterone than the aorta. Testosterone is a more potent relaxing agent of rabbit coronary artery than other testosterone analogues.

Effect of Sodium Carboxymethylcellulose on Post-Operative Peritoneal Adhesion Formation in Rabbits

Thirty non-pregnant female albino rabbits of the blanc du Bouscat strain were selected for this study. Laparotomies were performed on the animals. Both uterine horns of each animal were transected, then repaired by end-to-end anastomosis. Before closing the abdomen, 1% sodium carboxymethylcellulose (SCMC), 7 ml/kg body weight, was instilled in 20 animals (study group) and dextran 70, 7 ml/kg body weight, was instilled in the remaining 10 animals (control group). Two weeks later, the animals were re-explored and adhesion formations were assessed. It was found that SCMC reduced adhesion formation in the treated animals more than dextran 70.

Induction of Flavin-Containing Monooxygenase (FMO B) in Rabbit Lung and Kidney by Sex Steroids and Glucocorticoids

Modulation of lung and kidney levels of flavin-containing monooxygenase (FMO) isoform B following sc administration of dexamethasone, progesterone, β-estradiol, aldosterone, or β-estradiol plus progesterone was examined in male rabbits. Both dexamethasone and progesterone increased FMO B protein levels in lung. N-Oxygenation of N, N′-dimethylaniline (DMA) was significantly induced in lung microsomes from rabbits treated with progesterone. In kidney, only dexamethasone was effective in inducing FMO B protein levels and DMA N-oxygenation. Surgical implantation of osmotic pumps containing β-estradiol or progesterone into non-pregnant female rabbits resulted in elevated plasma levels of these steroids after 4-5 days at which point the lung levels of FMO B were induced by 35 and 82% for β-estradiol and progesterone, respectively. The responsiveness of FMO B in lung to both progesterone and glucocorticoids and in kidney to only the latter is consistent with the developmental pattern of both maternal FMO B and peak plasma levels of these steroids during pregnancy.

The pharmacokinetics and absorption of recombinant human relaxin in nonpregnant rabbits and rhesus monkeys after intravenous and intravaginal administration.

Recombinant human relaxin (rhRlx) is being developed as a potential cervical ripening agent to be applied intravaginally or intracervically prior to parturition. The pharmacokinetics and absorption of rhRlx were determined in nonpregnant female rabbits and rhesus monkeys after intravenous bolus (iv) and intravaginal administration of 0.1 mg/kg; additionally, rabbits were dosed with 0.5 mg/kg intravaginally. In rabbits (n = 6), mean (+/- SD) peak concentrations following iv bolus administration were 1554 +/- 296 ng/mL. The weight-normalized clearance (CL/W) was 5.9 +/- 0.4 mL/min/kg, initial volume of distribution (V1/W) was 57 +/- 9 mL/kg, and volume of distribution at steady state (Vss/W), assuming central compartment elimination, was 240 +/- 20 mL/kg. Vss/W could be as large as 2000 +/- 400 mL/kg without this assumption. The estimated amounts of rhRlx absorbed in rabbits following intravaginal administration of 0.1 and 0.5 mg/kg (n = 5/dose) were 3.1 +/- 1.4 and 0.7 +/- 0.3%, respectively; peak concentrations were 600 +/- 297 and 1066 +/- 584 pg/mL, respectively. In rhesus monkeys (n = 5) after iv administration, peak concentrations were 971 +/- 277 ng/mL; CL/W was 4.1 +/- 0.6 mL/min/kg, V1/W was 78 +/- 25 mL/kg, and Vss/W, assuming central compartment elimination, was 690 +/- 220 mL/kg. The upper limit for Vss/W was 1600 +/- 200 mL/kg when no assumptions were made regarding site (compartment) of elimination. After intravaginal administration (n = 6), two monkeys had undetectable rhRlx concentrations throughout the 48-hr sampling interval; one monkey had only one sample containing measurable rhRlx (51 pg/mL) at 24 hr; and three monkeys absorbed < 2% of the 0.1 mg/kg dose.(ABSTRACT TRUNCATED AT 250 WORDS)

HELLP syndrome-like biochemical parameters obtained with endothelin-1 injections in rabbits.

We studied the effects of bolus injections and infusion of endothelin-1 (ET-1) in female rabbits by measuring serum glutamic oxaloacetic transaminase (GOT), glutamic pyruvic transaminase (GPT), lactic dehydrogenase (LDH), antithrombin III (AT-III), thrombin antithrombin (TAT) complexes, platelet counts and indirect bilirubin. Two successive bolus doses of 0.125 and 0.25 nmol/kg of ET-1 with an interval of 30 min were given to conscious non-pregnant female rabbits (n = 8). GOT, GPT and LDH were found to be significantly increased after injections of ET-1 (p < 0.02, p < 0.04 and p < 0.05, respectively). The percent AT-III activity decreased significantly (p < 0.005). Vasospasm of the hepatic artery was demonstrated by angiography with the same bolus doses in rabbits. There was also an increase in GOT (p < 0.003), GTP (p < 0.05), LDH (p < 0.007), indirect bilirubin (p > 0.07) and TAT complexes (p < 0.02) and a decrease in AT-III (p < 0.03) and platelet counts (p < 0.02) in rabbits (n = 10) after 24 h of continuous infusion of ET-1 (0.6 nmol/kg/h). Histological examination of rabbit liver tissues showed varying degrees of ischemic necrosis of hepatocytes. Thus this study suggests that exogenously administered ET-1 causes vasospasm and liver ischemia resulting in HELLP syndrome-like blood parameters in rabbits.

Acute effect of 17 beta-estradiol on rabbit coronary artery contractile responses to endothelin-1.

We assessed the acute effect of 17 beta-estradiol on coronary artery constrictor responses to endothelin-1. 17 beta-Estradiol significantly shifted endothelin-1, calcium, or BAY K 8644 concentration-dependent contraction curves to the right in endothelium-denuded coronary arteries isolated from nonpregnant female rabbits. The -log 50% effective dose (ED50) of calcium in high KCl medium (100 mM) was 3.8 +/- 0.11 in control and 3.2 +/- 0.1 and 2.8 +/- 0.12 after incubation with 17 beta-estradiol (1 and 10 microM, respectively). The -log ED50 of BAY K 8644 (KCl 15 mM) was 7.8 +/- 0.1 in control and 7.4 +/- 0.08 and 7.2 +/- 0.05 in the presence of 17 beta-estradiol (1 and 10 microM, respectively). The -log ED50 of endothelin-1 was 9.2 +/- 0.08 in control and 8.8 +/- 0.1, 8.4 +/- 0.07, and 8.1 +/- 0.12 after incubation with 17 beta-estradiol (3, 10, and 30 microM, respectively). Similar results were obtained from coronary arteries of male rabbits. These increases of -log ED50 values were significant (P less than 0.05 or 0.01). 17 beta-Estradiol and verapamil induced dose-dependent relaxation in both endothelium-intact or -denuded coronary arteries submaximally precontracted by endothelin-1. NG-monomethyl-L-arginine had no effect on relaxation induced by 17 beta-estradiol, whereas it eliminated relaxation induced by acetylcholine in rings with an intact endothelium. These data suggest that 17 beta-estradiol attenuates the rabbit coronary artery contraction induced by endothelin-1 via an endothelium-independent mechanism, possibly by affecting calcium influx.

Effect of calcium on estrogen and follicle stimulating hormone secretion in rabbits

The effect of calcium gluconate on estrogen (estradiol) serum level as well as follicle stimulating hormone level was studied. Our results revealed that oral administration of calcium gluconate (100 mg/kg body weight) to adult non-pregnant female rabbits caused a significant increase of serum levels of estradiol and follicle stimulating hormone. On the other hand, oral contraceptive (Norminest tablets) decreased significantly follicle stimulating hormone serum level, while combined administration of calcium gluconate and oral contraceptive caused significant increase of serum level of follicle stimulating hormone compared with control values. Also, concurrent administration of calcium gluconate and Norminest tablet increased significantly the rate of conception compared with group received Norminest tablets only. These results indicated that combined administration of calcium and oral contraceptives must be cautiously.

Steroid hormones: modulators of Na+ absorption and Cl- secretion in cultured tracheal epithelia.

Cultures of tracheal epithelial cells from adult nonpregnant female rabbits maintained a different balance of Na+ absorption and Cl- secretion from cells of pregnant animals and fetal cultures. Cells of nonpregnant rabbits had a large Na+ absorptive current (11 microA/cm2 or 53% of baseline short circuit current) and a small Cl- secretory current (2.4 microA/cm2 or 11%). In contrast, fetal cells had greater Cl- secretion (15.1 microA/cm2 or 61%) and much less Na+ absorption (1.6 microA/cm2 or less than 10%). Cells of pregnant animals had amounts of Cl- secretion (11.4 microA/cm2 or 41%) and Na+ absorption (6.7 microA/cm2 or 22%) that were in between that of fetal and adult nonpregnant animals. In addition to these striking differences in baseline ion transport among the three groups, epinephrine was found to stimulate Cl- secretion in cells from pregnant rabbits, both Na+ absorption and Cl- secretion in cells from nonpregnant animals, and neither in fetal cells. Steroid hormones of pregnancy, progesterone and estradiol, when added to cells cultured from nonpregnant rabbits, altered the magnitudes of the individual transport pathways to mimic cells cultured from pregnant animals. In addition to changing baseline transport, these steroids modified the epinephrine-stimulated currents to resemble those in the fetus and in pregnancy. We conclude that steroid hormones regulate the balance of Na+ absorption and Cl- secretion in tracheal epithelia in utero and in adulthood.

Myo-inositol homeostasis in foetal rabbit lung.

In several species, lung maturation is accompanied by a decline in the phosphatidylinositol content of lung surfactant and a concomitant increase in its phosphatidylglycerol content. To examine the possibility that this developmental change is influenced by the availability of myo-inositol, potential sources of myo-inositol for the developing rabbit lung were investigated. On day 28 of gestation the myo-inositol content of foetal rabbit lung tissue (2.3+/-0.5mumol/g of tissue) was not significantly different from that of adult lung tissue but the activity of d-glucose 6-phosphate:1l-myo-inositol 1-phosphate cyclase (cyclase) in foetal lung tissue (81.0+/-9.0nmol.h(-1).g of tissue(-1)) was higher than that found in adult lung tissue (23.2+/-1.0nmol.h(-1).g of tissue(-1)). Day 28 foetal rabbit lung tissue was found also to take up myo-inositol by a specific, energy-dependent, Na(+)-requiring mechanism. Half-maximal uptake of myo-inositol by foetal rabbit lung slices was observed when the concentration of myo-inositol in the incubation medium was 85mum. When the myo-inositol concentration was 1mm (but not 100mum) the addition of glucose (5.5mm) stimulated myo-inositol uptake. myo-Inositol uptake was observed also in adult rabbit lung and was found to be sub-maximal at the concentration of myo-inositol found in adult rabbit serum. The concentration of myo-inositol in the serum of pregnant adult rabbits (47.5+/-5.5mum) was significantly lower than that of non-pregnant adult female rabbits (77.9+/-9.2mum). On day 28 of gestation the concentration of myo-inositol in foetal serum (175.1+/-12.0mum) was much less than on day 25, but more than that found on day 30. A transient post-partum increase in the concentration of myo-inositol in serum was followed by a rapid decline. Much of the myo-inositol in foetal rabbit serum probably originates from the placenta, where on day 28 of gestation a high cyclase activity (527+/-64nmol.h(-1).g of tissue(-1)) was measured. The gestational decline in serum myo-inositol concentration, together with the decreasing cyclase activity of the lungs, is consistent with the view that maturation of the lungs is accompanied by decreased availability of myo-inositol to this tissue.

Vitamin D metabolism in pregnant rabbits: differences between the maternal and fetal response to administration of large amounts of vitamin D3.

Maternal and fetal metabolism of vitamin D was examined in term pregnant rabbits fed a normal diet and in those supplemented with a large amount of vitamin D3. Term pregnant rabbits (27--30 days of gestation) fed the normal diet showed lower levels of plasma calcium, 25-hydroxyvitamin D3 (250HD3), and 24,25-dihydroxyvitamin D3 [24,25-(OH)2D3] and higher plasma 1 alpha, 25-dihydroxyvitamin D3 [1 alpha, 25-(OH)2D3] levels than age-matched nonpregnant female rabbits. Kidney homogenates from pregnant rabbits produced mainly 1 alpha 25-(OH)2D3, while those from nonpregnant animals produced 24,25-(OH)2D3 primarily. Plasma concentrations of calcium and phosphorus were significantly higher in fetuses than in mothers. Plasma levels of 250HD3 and 24,25-(OH)2D3 in fetuses were almost identical to those in mothers, whereas 1 alpha,25-(OH)2D3 levels in plasma were significantly higher in mothers than in their fetuses. A daily administration of 650 nmol vitamin D3 for 3 days to term pregnant rabbits caused a significant increase in calcium, phosphorus, 25OHD3, and 24,25-(OH)2D3 in maternal plasma, and in 25OHD3 and 24,25-(OH)2D3, but not calcium and phosphorus in fetal plasma. Treatment with large amounts of vitamin D3 also induced a marked suppression of 1 alpha-hydroxylase activity and a concomitant increase of 24-hydroxylase activity in the maternal but not in the fetal kidney. Plasma concentrations of 1 alpha,25-(OH)2D3 were not affected by treatment with large amounts of vitamin D3 in either the fetuses or the mothers. These results clearly indicate that the renal 25OHD3 metabolism in the fetus is regulated independently of that in the mother.