Maternal
melatonin influences rates of somatic and reproductive organs
postnatal development of male rat offspring Beatriz Díaz, Elena Díaz,
Mª Dolores Colmenero, Agustin Arce,
Ana Esquifino & Bernardo Marín
Abstract
Female rat dams, housed in 12L:12D photoperiod, were pinealectomized
or injected daily 1½ h before onset of darkness with 250
mg melatonin/100 g BW., during pregnancy; control and pinealectomized
dams received a placebo. Somatic, reproductive organs and gonadotropins
levels luteinizing hormone (LH) and follicle stimulating hormone
(FSH) of male offspring were examined at the following phases
of their sexual development: neonate, infantile, juvenile or prepubertal
and pubertal periods. Pinealectomy of the mother produced an altered
developmental pattern in the offspring (PIN-X offspring). During
the infantile period when pups are lacking maternal melatonin
and their own melatonin rhythm is not yet established, a delayed
growth of body and testis weights was observed. After the second
week of life, from 15 to 25 days of age, coinciding with the initiation
of the melatonin rhythm, a speed-up growth of body and testes
was observed, followed by a delayed growth from 25 to 30 days,
in the juvenile period; this also coinciding with reduced LH levels
observed at 30 days of age. Indeed, in PIN-X offspring significantly
greater growth rate was observed during the pubertal period than
in control offspring, which could be due to the increase in LH
secretion up to normal values observed in the PIN-X offspring.
Seminal vesicles of the PIN-X offspring also showed delayed growth,
which was overcome at the pubertal period. Melatonin (MEL) treatment
during pregnancy produced minor alterations in postnatal development
of the reproductive tract. Only increased pituitary gland weight
was observed at 15 and decreased at 25 days of age. At 25 days
of age, MEL offspring reached the highest LH values, and at 30
days of age, PIN-X offspring still show low values. Which suggests
that other factors than the endocrine activity of the gland are
affecting the somatic growth of the pituitary gland. Seminal vesicles
weight was delayed at 25 days of age in the MEL offspring. These
results indicate that maternal melatonin is necessary for a normal
somatic growth and postnatal development of reproductive organs
of the offspring.
