Role of fetal skin in circulation of amniotic fluid

Evaluation of Biochemical Composition of Amniotic and Allantoic Fluids at Different Stages of Pregnancy in Queens

Simple Summary

Fetal fluid contents influence growth and development, fetal wellbeing and a protection mechanism for the fetus itself. Very little is known about the composition of fetal fluids during pregnancy in cats and about changes in contents that occur throughout gestation. In this study, initial results regarding the biochemical composition of fetal fluids are provided. A comparison with maternal serum was also performed. A complete understanding of trends can be helpful for the early detection of some pathologies during pregnancy, such as in humans and mares.

Abstract

Fetal fluid contents have functions in protecting fetuses and are essential for fetal development and maturation. However, little is known about the exact physiological functions of fetal fluids in fetal development, as well as the changing composition throughout the gestational period in cats. In this study, the biochemical composition of amniotic (AMN) and allantoic (ALL) fluids was investigated, as well as in the maternal serum of pregnant queens. Eighteen queens were included in this study and assigned to six different groups, D₂₀, D₂₅, D₃₀, D₄₀, D₄₅ and D₆₀, according to the gestational stage of fetal development. A total of 44 amniotic and 37 allantoic samples were collected. Fetal fluids contained lesser concentrations of alanine aminotransferase, albumin, cholesterol, triglycerides, creatine kinase, amylase, total protein and globulin than maternal serum. Other variables, such as aspartate aminotransferase, gamma-glutamyl transferase, bilirubin and alkaline phosphatase, were in different concentrations at specific stages of gestation when compared to maternal serum. There were no differences between fetal fluids and maternal serum for lactate dehydrogenase, urea, lipase or glucose concentrations. There were greater concentrations of creatinine in amniotic fluid than in allantoic fluid or maternal serum. Based on the results of this study, fetal fluids do not accumulate as a result of the simple filtration of maternal blood, but rather, the fetus produces many of these components as a consequence of organ development and maturation.

IGF-I and NEFA concentrations in fetal fluids of term pregnancy dogs

Insulin-like growth factor-I (IGF-I) and non-esterified fatty acids (NEFA) play an essential role in fetal growth and development. To date, fetal fluids IGF-I and NEFA levels at term canine pregnancy are unknown and could be related to the neonatal development and breed size. For these reasons, the aims of the present study were as follows: (1) to evaluate IGF-I and NEFA concentrations in fetal fluids collected from normally developed and viable newborn puppies born at term of normal pregnancies; (2) to assess possible differences between IGF-I and NEFA levels in amniotic compared with allantoic fluid; (3) to detect possible relationship between breed body size and IGF-I and NEFA amniotic and allantoic concentrations; (4) to evaluate possible differences in IGF-I fetal fluids levels between male and female puppies; and (5) to assess possible correlations between the two hormones in each type of fluid. The study enrolled 25 pure breed bitches submitted to elective Cesarean section at term because of the high risk of dystocia or previous troubles at parturition. At surgery, amniotic and allantoic fluids were collected and assayed for IGF-I and NEFA. IGF-I and NEFA amounts in both amniotic and allantoic fluids of different breed size bitches (small: ≤10 kg; medium: 11-25 kg; large: 26-40 kg) were detected, as well as the effect of gender on IGF-I levels. On a total of 73 amniotic and 76 allantoic samples collected by normal, viable, and mature newborns, the mean IGF-I concentration was significantly higher in amniotic than in allantoic fluid in all three groups, but the amniotic IGF-I levels were significantly lower in small and medium size bitches when compared with large ones. No significant differences were found in allantoic IGF-I concentrations among size groups. A significant effect of the puppy gender on IGF-I content in both fetal fluids was not reported. Regarding NEFA, in all the three groups, the mean NEFA concentration did not significantly differ between amnion and allantois, but in both fetal fluids, higher NEFA levels were detected in samples belonging to small breeds when compared with medium and large. These data strongly indicated that, also in the dog, a relation between fetal fluids IGF-I and NEFA concentrations and breed size exists. Further research is needed to elucidate the possible role of IGF-I and NEFA in the pathologic conditions related to canine fetal growth.

Modulation of the biochemical composition of amniotic and allantoic fluids as a control mechanism of feline foetal development

Amniotic fluid exerts a protective function and is an essential component for foetal development and maturation during pregnancy. However, little is known about the exact physiological functions of foetal fluids in this process as well as their biochemical composition in cats. In the present study, the biochemical composition of amniotic and allantoic fluids and maternal serum in pregnant queens was compared after performing an ovariohysterectomy. Fifteen queens were included in the study and distributed in four different groups, D(30), D(40), D(50) and D(60), according to their gestational age. Foetal fluids showed thoroughly greater concentrations of dissociate and total bilirubin, bile acids and gamma-glutamyl transferase than those of maternal serum, whereas albumin, total protein, alanine-transferase, creatine-kinase, amylase, lipase, triglycerides, cholesterol, HDL-cholesterol, and LDL-cholesterol were significantly lower, as compared to maternal serum. Other parameters like alkaline phosphatase, uric acid, creatinine, and electrolytes showed significant differences at specific stages of pregnancy, when compared to maternal serum. Lactate and cortisol significantly increased at the end of the pregnancy in foetal fluids, when compared with maternal serum. No significant differences between foetal fluids and maternal serum were observed for aspartate aminotransferase, lactate dehydrogenase, urea, phosphorus and glucose. According to our results, foetal fluids composition is not a result of simple filtration from maternal blood, the fetus being an active element involved in the production of the same and reflecting organ development and maturation.

In utero domoic acid toxicity: a fetal basis to adult disease in the California sea lion (Zalophus californianus)

California sea lions have been a repeated subject of investigation for early life toxicity, which has been documented to occur with increasing frequency from late February through mid-May in association with organochlorine (PCB and DDT) poisoning and infectious disease in the 1970’s and domoic acid poisoning in the last decade. The mass early life mortality events result from the concentrated breeding grounds and synchronization of reproduction over a 28 day post partum estrus cycle and 11 month in utero phase. This physiological synchronization is triggered by a decreasing photoperiod of 11.48 h/day that occurs approximately 90 days after conception at the major California breeding grounds. The photoperiod trigger activates implantation of embryos to proceed with development for the next 242 days until birth. Embryonic diapause is a selectable trait thought to optimize timing for food utilization and male migratory patterns; yet from the toxicological perspective presented here also serves to synchronize developmental toxicity of pulsed environmental events such as domoic acid poisoning. Research studies in laboratory animals have defined age-dependent neurotoxic effects during development and windows of susceptibility to domoic acid exposure. This review will evaluate experimental domoic acid neurotoxicity in developing rodents and, aided by comparative allometric projections, will analyze potential prenatal toxicity and exposure susceptibility in the California sea lion. This analysis should provide a useful tool to forecast fetal toxicity and understand the impact of fetal toxicity on adult disease of the California sea lion.

Aquaporins in development -- a review

Water homeostasis during fetal development is of crucial physiologic importance. It depends upon maternal fetal fluid exchange at the placenta and fetal membranes, and some exchange between fetus and amniotic fluid can occur across the skin before full keratinization. Lungs only grow and develop normally with fluid secretion, and there is evidence that cerebral spinal fluid formation is important in normal brain development. The aquaporins are a growing family of molecular water channels, the ontogeny of which is starting to be explored. One question that is of particular importance is how well does the rodent (mouse, rat) fetus serve as a model for long-gestation mammals such as sheep and human? This is particularly important for organs such as the lung and the kidney, whose development before birth is very much less in rodents than in the long-gestation species.