Studies on reproductive endocrine function in rats treated with monosodium l-glutamate early in life

Abstract

Repeated s.c. injections of high doses of monosodium-l-glutamate (MSG) to neonatal female rats caused precocious puberty, disturbed oestrous cycle and small ovaries and pituitary. Pituitary LH and FSH were low but the basal serum levels were unchanged from control values. Serum E₂ level was significantly low in the early stages. Cyclic regulation of gonadotrophin release and follicular maturation was inadequate. Pituitary-gonadal function in males was less affected. Females treated with high doses of MSG as infants showed normal onset of puberty and regular oestrous cycles, but subsequent earlier oestrous cycle irregularity was observed than in controls. Gonadal weights in both sexes were slightly reduced. Serum hormone levels and the pituitary contents were not changed from those of controls except for reduced FSH. Males and females, given subneurotoxic doses of MSG, or fed large amounts of MSG ad libitum, presented no abnormalities. MSG administration therefore induces marked abnormalities in reproductive endocrine function after maturation only when injected parenterally, early in postnatal life, in repeated, very large doses.