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Metabolism of Rat ₁-Fetoprotein¹

Division of Clinical Immunology and Allergy, McGill University Clinic [B. C., P. G., D. D. O., J. S.], and the Department of Urology [W. B.], Montreal General Hospital, Montreal, Quebec, Canada

The pattern of ₁-fetoprotein (AFP) disappearance from the rat circulation has been examined by radioimmunoassay in females in both the postpartum and postabortion periods, in males and nulliparous females infused with AFP-rich rat amniotic fluid, and in neonatal rats during the first 44 days after birth. The half-life of AFP in the postgestational female rat was 22 to 24 hr and was not significantly different from that observed in either male or nulliparous female rats. This finding indicates that AFP fails to evoke an immune response in the adult animal, and suggests that low concentrations of AFP persist in the circulations of mature rats. The biphasic pattern of AFP disappearance from the circulation of the neonatal rat indicates that during the first 26 days of the newborn period, there is either continued AFP synthesis, immaturity of the catabolic mechanisms for degrading AFP, or both. The adult pattern of AFP disappearance begins on the 26th day of life, and circulating AFP concentrations fall to the adult range by the 44th day after birth.

¹ Supported by grants from the Medical Research Council of Canada, Ottawa, Ontario; the National Cancer Institute of Canada, Toronto, Ontario; and the Cancer Research Society, Inc., Montreal, Quebec, Canada.

² To whom reprint requests should be addressed, at Division of Clinical Immunology and Allergy, Room 7135, Montreal General Hospital, 1650 Cedar Avenue, Montreal, Quebec, H3G 1A4, Canada.

Received 3/29/74. Accepted 6/ 7/74.