IRREVERSIBLE INHIBITION OF PITUITARY PROLACTIN AND GROWTH HORMONE SECRETION AND OF MAMMARY GLAND DEVELOPMENT IN MICE BY MONOSODIUM GLUTAMATE ADMINISTERED NEONATALLY

Abstract

ABSTRACT A single subcutaneous injection of 4 mg monosodium glutamate (MSG) to neonatal female mice resulted in obesity when the mice became adult. The MSG-treated mice had significantly smaller contents of prolactin and growth hormone (GH) in the pituitary, as compared with the controls at 60, 150 and 420 days of age except for the content of prolactin at 60 days of age. The development of normal and pre-neoplastic mammary systems was markedly suppressed in the MSG-treated mice at 150 and 420 days of age. The oestrous cycles of the MSG-treated mice showed longed periods of oestrus and shorter periods of dioestrus than those of the controls. The pituitary weight was significantly smaller in the MSG-treated mice than in the controls at 60 and 150 days of age. The weights of several other organs showed no difference between the groups at any of the ages examined. These results indicate that MSG inhibits the pituitary secretion of prolactin and GH through its deleterious effects on the hypothalamus and that the effects are irreversible.