Hair dehydroepiandrosterone (DHEA) concentrations in newborn dogs

The last intrauterine foetal stage of development and the neonatal period represent the most challenging phases for the mammals offspring. During this time-frame the hypothalamic-pituitary-adrenal axis (HPA) is a key system regulating several physiologic processes, such as the foetal multi-organs final maturation, the response to stress, and after birth the HPA keeps a role in the neonatal adaptation to the extra-uterine life. Apart of cortisol, in response to the adrenocorticotrophic hormone, the adrenals produce dehydroepiandrosterone (DHEA). Some studies in humans and other animal species demonstrated that the foetal pituitary-adrenal axis secretes DHEA under activation from maternal cortisol. Thus, DHEA measured at birth in newborns could be considered as a marker of offspring HPA activity, under the maternal influence. HPA activity, in foetus as well as in newborns, was previously investigated by foetal blood or cord blood analysis, but these methods were limited due to the invasiveness of sampling and to the single point measurements. Non invasive, and long time-frame retrospective hormonal levels analysis were performed in the hair of humans and animals, but not in the hair of newborn puppies, and DHEA never investigated in puppies, at the authors knowledge. This study was aimed to assess DHEA concentrations in the hair of newborn puppies, and to evaluate the possible influence of newborn age and gender, and breed size on DHEA concentrations.The study enrolled 116 spontaneously dead purebred puppies, 55 females and 61 males. According to maternal body weight, puppies were classified as belonging to small size breeds (bodyweight ≤10 kg) (N = 48), or to a merged class of medium and large size breeds (bodyweight >10 kg) (N = 68). Based on the age at death, all newborns were grouped in three classes of age, as follows: 1) premature: when puppies were delivered between 2 and 1 weeks before the expected date of whelping, estimated by ultrasonographic parturition date prediction [1] (N=19); 2) fresh, term born dead puppies (puppies delivered dead at the predicted term of pregnancy and puppies born alive at term, but dead within 24 hours since birth (N=79); 3) puppies dead between 1 and 30 days of age (N=28). Hair samples were collected from each puppy by shaving, and stored at room temperature until analysis by RIA [2]. In the hair of the 116 puppies, the overall DHEA concentration was 46.8±14.8 pg/mg. According to newborn gender, DHEA levels were 48.6±15.66 pg/mg in females vs 45.1±13.73 pg/mg in males, without significant differences. In relation to breed size, DHEA levels were 45.5±13.61 pg/mg in small size breed puppies compared to 47.8±15.61 pg/mg in medium-large size breed puppies, with no significant differences. According to age at death, DHEA hair concentrations in premature puppies (52.5±15.12 pg/mg) were significant higher (p<0.05) than in puppies dead between 1 and 30 days after birth (44.5±17.78 pg/mg), but similar to fresh term born dead puppies (46.2±16.5 pg/mg). This study demonstrated that DHEA is quantifiable in the hair of newborn dogs, and interesting for non invasive, long time-frame foetal and neonatal studies also in this specie. The results obtained from 116 newborns evidenced that only the newborn age influenced DHEA, while newborn gender or breed body size did not. The effect of age is in agreement with different DHEA plasma concentrations reported, according to age, in adult dogs, while the absence of significant influence of sex disagree with data reported for adult dogs [3], maybe because of the very young age of the studied puppies.