Effect of pinealectomy and melatonin treatment during pregnancy on the sexual development of the female and male rat offspring

Abstract

Díaz López B, Colmenero Urquijo MD, Díaz Rodriguez ME, Arce Fraguas A, Esquifino Parras A, Marín Fernández B, Effect of pinealectomy and melatonin treatment during pregnancy on the sexual development of the female and male rat offspring. Eur J Endocrinol 1995;132:765–70. ISSN 0804–4643 Sexual development of female and male rat offspring of control, pinealectomized (PIN-X) or melatonin (MEL 2 50 μg/100 g body wt)-treated mother rats during pregnancy was studied. Newborns were studied at the following phases of sexual development: neonate (5 days old), infantile (15 days old), juvenile (25 and 30 days old) and pubertal phase (55 days). In female offspring, MEL treatment during pregnancy significantly increased plasma luteinizing hormone (LH) in 15- and 25-day-old rats; however, at the end of the prepubertal period (30 days) the concentration of plasma LH decreased significantly as compared to control rats. This hormonal pattern was different from that observed in offspring of control and PIN-X rats, which had low LH levels at 25 days of age and higher LH levels at 30 days of age. Follicle-stimulating hormone (FSH) did not vary significantly among the three groups. Plasma prolactin levels were affected by PIN-X of the mother, showing significantly higher levels in the 5-day-old offspring than in the controls; plasma prolactin levels were also affected by MEL treatment of the mother, producing hyperprolactinemia in the 30-day-old female offspring. In male offspring, sexual development in control male rats progressed rapidly with significantly increased LH and FSH levels at 25 and 30 days compared to those measured during the neonatal and infantile periods. Pinealectomy of the mother induced the following modifications: in 5-, 15- and 30-day-old male rats, decreased LH levels were measured relative to the other two groups studied in 5- and 25-day-old rats, significantly lower FSH levels than in the control rats were recorded. However, in 5- and 15-day-old rats, significantly higher prolactin levels than in control rats were measured. Melatonin injections during pregnancy decreased FSH levels at 5, 25, 30 and 55 days as compared to the control males. Also, MEL increased LH levels in 25-day-old rats and significantly decreased prolactin levels in 15- and 55-day-old rats as compared to the other two groups. These results indicate that the mother's pineal gland and MEL treatment can act on fetal development and influence the postnatal ontogeny of the hormones involved in the neuroendocrine–reproductive axis in developing rats. The effect of MEL was apparent during pubertal stages of the offspring, while the effect of PIN-X was more apparent during the juvenile period of the young rats. Beatriz Díaz López, Dpt. Biología Funcional, Arca Fisiología, Fac, Medicina, Universidad de Oviedo, 33006-Oviedo, Spain