INCREASED NUMBERS OF SERTOLI AND GERM-CELLS IN ADULT-RAT TESTES INDUCED BY SYNERGISTIC ACTION OF TRANSIENT NEONATAL-HYPOTHYROIDISM AND NEONATAL HEMICASTRATION

The combined effects of transient neonatal hypothyroidism and neonatal hemicastration were investigated to see whether they were additive. H ypothyroidism was induced in litters of ten male rats for 25 days from the day of birth by administration of 0.1% (w/v) 6-propyl-2-thiouraci l in the mother's drinking water; hemicastration was performed on the day of birth. Controls included both normal and sham-operated animals. Numbers of Sertoli cells and round spermatids were quantified at age 135 days using stereological methods. Sham-operation had no effect on testis mass, or numbers of Sertoli or germ cells. Transient neonatal h ypothyroidism resulted in an increase in testicular mass of 27% (P < 0 .05), whereas neonatal hemicastration resulted in a 33% (P < 0.05) inc rease over control; the combination of the two procedures resulted in a 62% (P < 0.05) increase. There were corresponding significant increa ses in the number of Sertoli cells: 82% with hypothyroidism, 18% with hemicastration and 123% with the combination of the two procedures. Nu mbers of round spermatids showed similar increases: 59% with hypothyro idism, 45% with hemicastration and 95% with the combination of the two procedures. It is concluded that the effects of the combination of tr ansient neonatal hypothyroidism and hemicastration are additive with r espect to testicular mass, and numbers of Sertoli and germ cells.