Enhancement of seminiferous tubular growth and spermatogenesis in testes of rats recovering from early hypothyroidism: a quantitative study.
Testicular weight and DNA content were markedly reduced (63 and 69%) in weanling Long-Evans rat pups rendered hypothyroid from birth by administration of propylthiouracil (PTU), a reversible goitrogen. These growth deficits worsened to > 80% by continuing hypothyroidism beyond weaning, to days 50 and 90. Recovery of thyroid function, brought about by discontinuing PTU at weaning, resulted in a paradoxical stimulation of testis growth, amounting to increased weight (40%), DNA content (60%) and size by 90 days, compared to age-matched controls. In the 25-day or older hypothyroid rats, testicular structure was immature and spermatogenesis markedly delayed, as evident by closed lumen and significantly reduced diameter of seminiferous tubules (38%), thickness of germinal layer (70%), and number of primary spermatocytes (86%), compared to control. Hypothyroidism did not alter the number of tubules per testis cross section. In the 90-day recovery rats, numbers of seminiferous tubules were unchanged but tubular diameter was significantly (20%) larger than in controls and spermatogenesis appeared very active as indicated by significantly increased germinal layer thickness (22%) and total number and density of primary spermatocytes (55% and 40%). The results show that although postnatal hypothyroidism is deleterious for testicular growth and spermatogenesis, recovery from this condition leads to enhanced seminiferous tubular growth and spermatogenesis.
Meisami
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E
Division of Developmental and Cell Biology, University of California, Berkeley 94720.
Najafi
A
A
Timiras
P S
PS
D000818:Animals; D000831:Animals, Newborn; D004247:DNA / Q000032:analysis; D007037:Hypothyroidism / Q000139:chemically induced / Q000473:pathology / Q000503:physiopathology*; D008297:Male; D009929:Organ Size; D011441:Propylthiouracil; D051381:Rats; D012671:Seminiferous Tubules / Q000254:growth & development* / Q000473:pathology; D013090:Spermatocytes; D013091:Spermatogenesis; D013737:Testis / Q000737:chemistry / Q000254:growth & development / Q000473:pathology
D011441:Propylthiouracil; D004247:DNA