Preliminary report on the effects of totigestational exposure to ethchlorvynol.

Ethchlorvynol, a sedative-hypnotic drug used clinically since 1955, has recently been the subject of renewed interest primarily because of its chemical relationship to vinyl chloride. In our totigestational studies, sperm-positive female rats were given a daily dose of ethchlorvynol dissolved in olive oil for 21 consecutive days. The dams were allowed to deliver and their offspring were observed for alterations in development by monitoring a number of gross behavioral, histological and biochemical parameters at newborn, weanling, puberty, adult and geriatric stages. Gross development appeared normal at time of weaning: however, offspring of treated dams showed increased behavioral activity in addition to alterations in a number of clinical chemistry parameters. The dose-response seen with most of the parameters suggests that the changes are drug related. However, the clinical pathological significance has not been ascertained.

Preliminary Report on the Effects of Totigestational Exposure to Ethchlorvynol by Marvin A. Peters* and Pearlie M. Hudson* Ethchlorvynol, a sedative-hypnotic drug used clinically since 1955, has recendy been the subject of renewed interest primarily because of its chemical relationship to vinyl chloride. In our totigestational studies, sperm-positive female rats were given a daily dose of ethchlorvynol dissolved in olive oil for 21 consecutive days. The dams were allowed to deliver and their offspring were observed for alterations in development by monitoring a number of gross behavioral, histological and biochemical parameters at newborn, weanling, puberty, adult and geriatric stages. Gross development appeared normal at time of weaning; however, offspring of treated dams showed increased behavioral activity in addition to alterations in a number of clinical chemistry parameters. The dose-response seen with most of the parameters suggests that the changes are drug related. However, the clinical pathological significance has not been ascertained.
There are numbers of studies tying vinyl chloride exposure to angiosarcoma of the liver (1, 2), other hepatic diseases (3,4), chromosome aberrations (5), alterations in spleen (6), and pulmonary function (7), in addition to other pathological processes. All of these observations place an urgency in studying the mechanisms and far reaching consequences of this and related compounds.
Ethchlorvynol is a chemical somewhat related to vinyl chloride which has the capacity for altering the function of many physiological processes, most of which have been related to its CNS depressant and skeletal muscle-relaxant effects. It was introduced in 1955 as a clinically useful sedativehypnotic under the trade name Placidyl and has competed quite effectively with the barbituric acid derivatives in some areas. The physiological and biochemical mechanisms by which these effects are elicited have not been well defined. Only as recently as the early 70's has there been any significant attempt to understand it's disposition in either animals or man.
Cummins et al. (8), in a clinical study showed that the half-life of absorption for ethchlorvynol is approximately 0.3 hr. The decline in serum levels of the drug was found to be biphasic, suggesting that it is stored, most likely in adipose tissue compartments. On assuming a two-compartment model, the rate constant of elimination was calculated to be 0.13 hr. Cummins also found that ethchlorvynol was readily metabolized in the liver with only 0.025% of the dose excreted unchanged or as the glucuronide.
Another disposition study, perhaps a little more applicable to our work, was reported by Hume et al. (9). These investigators showed that an oral dose of ethchlorvynol given to pregnant dogs is rapidly absorbed and readily distributed to the fetal circulation in concentrations comparable to that found in the maternal blood. Little if any delay was seen in the drug reaching the fetal compartment. The various metabolites of ethchlorvynol have not been identified; however from the chemical struc-tUre. one might think conjugation as the glucuronide would be very likely. However, this metabolite has been looked forbut has not been found. Other possi'ble metabolites. such as other conjugates, a cy- clized five-membered ring, or products of hydroxyylation, reduction of unsaturated bonds, splitting off of HCI or vinyl chloride, etc. need to be considered. However, none of these metabolites has been identified. Our studies on the transplacental pathology of ethchlorvynol were initiated because of: The lack of information of transplacental effects on development and the potential for long term pathology in the offspring, the clinical usage in humans, the absence of metabolite information associated with the possibility of the vinyl chloride moiety of ethchlorvynol reacting in a similar way to vinyl chloride in the intact molecule or as a metabolite, and the occurrence of other unexplained complications associated with ethchlorvynol therapy.
Our studies, which are just beginning, are designed to provide information on the effect of ethchlorvynol on offspring of females subjected to totigestational exposure. Sperm-positive female rats were divided into three groups, and each group was given a daily oral dose of olive oil (control) or 20 or 80 mg/kg ethchlorvynol dissolved in olive oil for 21 days. The dams were allowed to deliver and raise their offspring. The offspring were observed for gross abnormalities and subjected to a number of behavioral, developmental, histological, and biochemical tests at various stages of development. The specific parameters monitored are shown in Tables 1-7. The data presented in the tables are for the most part as the means + S.E. Control-treated comparisons were made using Student's t; the level of significance is p < 0.05. Table 1 presents maternal and newborn statistics. No significant differences were seen between control and treated groups, however treated animals tend to be slightly heavier by 3 to 4 weeks.   Table 3 shows no difference in control versus treated groups in the three physiological parameters studied. However, treatment causes a trend toward decreased time for righting, suggesting increased activity in the offspring.
The results of behavioral tests are seen in Table  4, which shows a dose-response increased exploratory activity in both male and female weanling animals. Treated male animals tend to require less time to run the food maze with fewer mistakes than do the controls; however a dose response was not seen. Treated females were practically identical to the control females.
Clinical chemistry and hematological observations in weanling animals are presented in Tables 5  and 6. Several parameters-blood glucose, chloride, albumin, total bilirubin, SGOT, acid-base balance, and creatine phosphokinase-were all dLength of time animals would adhere to a screen inclined at 450 angle (7 days) or at a 750 angle (14 days).  December 1977 statistically different from those at the controls. A number of the parameters showed a dose-response relationship which supports the idea of a drugrelated effect. However, the biological significance is not obvious at this point in our experiments. A repetition of these results in another group of weanling animals or in animals of puberty age would add to the significance of these results.
No changes were seen in the hematological parameters. In animals autopsied at 5 weeks of age the 80 mg/kg treatment group was significantly heavier than the control, while the 20 mg/kg group was intermediate (Table 7). It is interesting to note that the mean weight of the brain, pituitary, thyroid, liver, epididymis, and uterus was smaller in the 80 mg/kg-treated animals than in the controls, in spite of the increased body weight.
As pointed out earlier, these data are preliminary and need to be repeated in another group of wean-!ing animals or supported by data from pubertyaged animals. Data just obtained in puberty animals tend to confirm the idea that totigestational treatment with ethchlorvynol causes increased activity in the offspring and further suggest that the increased activity may be of a somewhat random nature.