Maternal pineal gland participates in prepubertal rats' ovarian oocyte development.
BACKGROUND
Sexual maturation is a very complex phenomenom that it is mediated by the ontogeny of the hypothalamus-pituitary-gonadal axis during intrauterine life. The maternal pineal gland can affect fetal development because the main pineal hormone, melatonin, crosses the placental barrier. We found that melatonin treatment during gestation in the rat produced delayed sexual maturation of the female offspring. The present work was undertaken to study the maturational stage of oocytes of prepubertal female rats when their mothers were either pinealectomized (PIN-X) or treated with melatonin (MEL) during pregnancy.


METHODS
Three groups of female Wistar rats were used: control, PIN-X, and those treated (250 micrograms/100 g body weight) with melatonin throughout pregnancy. Ovaries of 25-30- and 34-day-old female offspring were studied during the prepubertal phase. Morphometric studies of semithin sections (1 micron) of the ovaries were performed. Oocyte, nuclear, and nucleolar volumes were calculated by a computer-assisted program (M.I.P.) in an image analyzer Kontron. Regularity of the structures was determined by the frequency distributions of circular and regular form factors.


RESULTS
Cytometric study of oocyte structure showed a frequency distribution of regular and circular form factors, with a high degree of regularity very close to unit. Cellular and nuclear volumes of follicular oocytes showed a transitory increase at 30 days of age in control rats. In the offspring of MEL-treated mother rats, a pattern of oocyte development showed significantly lower nuclear and nucleolar volumes at 30 days of age than at the other time points and significantly lower cellular volume at 34 days of age than at 25 days of age. In the offspring of PIN-X mother rats, no significant differences in oocyte cellular volumes were observed throughout prepubertal development, but we observed a significantly higher nuclear volume at 25 days of age and a significantly lower nucleolar volume at 30 days of age.


CONCLUSIONS
These findings show that the maternal pineal gland participates in cellular and nuclear volumes of prepubertal oocyte development. Melatonin treatment during pregnancy resulted in a redirected postnatal oocyte development.
Fernández
B
B
Departamentos de Morfología y Biología Celular, Facultad de Medicina,Universidad de Oviedo, Spain.
Díaz
E
E
Colmenero
M D
MD
Díaz
B
B
D000818:Animals; D005260:Female; D008550:Melatonin / Q000494:pharmacology; D009865:Oocytes / Q000187:drug effects / Q000254:growth & development*; D010870:Pineal Gland / Q000502:physiology* / Q000601:surgery; D011247:Pregnancy; D011297:Prenatal Exposure Delayed Effects; D051381:Rats; D017208:Rats, Wistar; D012741:Sexual Maturation / Q000502:physiology
D008550:Melatonin