Abstract
Summary
Neonatally castrated male rats (some bearing ovarian transplants) and female rats given testicular grafts at birth were injected chronically with 131I-labeled L-T4 and carrier T4 as adults; the radioactivity in plasma and kidneys was measured and compared with that in normal adult males and females. Both renal and plasma radioactivity were significantly higher in normal male rats than in females. Neonatally castrated males as well as females given testicular transplants at birth exhibited an increase in renal T4 to levels of normal males whereas neonatally castrated males bearing sc ovarian transplants showed a significant reduction in renal retention of T4. A sex difference in the capacity of the kidney to concentrate radiothyroxine was demonstrated. This was not solely related to adult androgen levels and was influenced by neonatal hormonal manipulations which are known to alter hypothalamic-pituitary relationships in the adult rat.
The skilled technical assistance of Mr. Phil Cooper and Mrs. Joy Ewing is most gratefully acknowledged. Statistical analyses were done with the program EXBIOL on file at the Common Research Computer Facility, Texas Medical Center, Houston, Texas. The authors are indebted to Dr. Edvart Sakiz for this program.
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